Former Vice President Joe Biden, Senator Bernie Sanders and Senator Amy Klobuchar listen as PBS anchor Judy Woodruff moderates the Democratic U.S. presidential candidates at Loyola Marymount University in Los Angeles, California, U.S., December 19, 2019. REUTERS/Mike Blake

The Audi PB18 e-tron is seen during the first press day of the Paris auto show, in Paris, France, October 2, 2018. REUTERS/Benoit Tessier

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Actress Michelle Dockery from the PBS series "Downton Abbey" arrives at the 68th Primetime Emmy Awards in Los Angeles, California U.S., September 18, 2016. REUTERS/Lucy Nicholson

British actress Laura Carmichael, of the PBS series "Downton Abbey," arrives at the 68th Primetime Emmy Awards in Los Angeles, California U.S., September 18, 2016. REUTERS/Lucy Nicholson

British actress Laura Carmichael, of the PBS series "Downton Abbey," arrives at the 68th Primetime Emmy Awards in Los Angeles, California U.S., September 18, 2016. REUTERS/Lucy Nicholson

British actress Laura Carmichael, of the PBS series "Downton Abbey," arrives at the 68th Primetime Emmy Awards in Los Angeles, California U.S., September 18, 2016. REUTERS/Lucy Nicholson

British actress Joanne Froggatt, of the PBS series "Downton Abbey," arrives at the 68th Primetime Emmy Awards in Los Angeles, California, U.S., September 18, 2016. REUTERS/Lucy Nicholson

British actress Joanne Froggatt, of the PBS series "Downton Abbey," arrives at the 68th Primetime Emmy Awards in Los Angeles, California, U.S., September 18, 2016. REUTERS/Lucy Nicholson

British actress Joanne Froggatt, of the PBS series "Downton Abbey," arrives at the 68th Primetime Emmy Awards in Los Angeles, California, U.S., September 18, 2016. REUTERS/Lucy Nicholson

U.S. President Barack Obama removes his jacked after an interview with PBS NewsHour co-anchor and managing editor Gwen Ifill (L) during a visit to Elkhart, Indiana, U.S. June 1, 2016. REUTERS/Kevin Lamarque

U.S. President Barack Obama gets his microphone fitted to participate in a town hall hosted by PBS during a visit to Elkhart, Indiana, U.S. June 1, 2016. REUTERS/Kevin Lamarque

U.S. President Barack Obama gets his microphone fitted to participate in a town hall hosted by PBS during a visit to Elkhart, Indiana, U.S. June 1 2016. REUTERS/Kevin Lamarque

Democratic U.S. presidential candidate former Secretary of State Hillary Clinton poses for a picture with a member of the audience at the conclusion of the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Democratic U.S. presidential candidates Senator Bernie Sanders and former Secretary of State Hillary Clinton greet members of the audience at the conclusion of the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Democratic U.S. presidential candidates Senator Bernie Sanders and former Secretary of State Hillary Clinton greet members of the audience at the conclusion of the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Democratic U.S. presidential candidate Senator Bernie Sanders poses for a picture with a member of the audience at the conclusion of the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Democratic U.S. presidential candidates Senator Bernie Sanders and former Secretary of State Hillary Clinton (R) shake hands with moderator Judy Woodruff at the conclusion of the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Democratic U.S. presidential candidate former Secretary of State Hillary Clinton speaks at the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Democratic U.S. presidential candidate former Secretary of State Hillary Clinton speaks at the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Democratic U.S. presidential candidate Senator Bernie Sanders speaks at the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Democratic U.S. presidential candidates Senator Bernie Sanders and former Secretary of State Hillary Clinton arrive on stage before of the start of the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young TPX IMAGES OF THE DAY

Democratic U.S. presidential candidates Senator Bernie Sanders and former Secretary of State Hillary Clinton wave as they arrive on stage before of the start of the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young TPX IMAGES OF THE DAY

Democratic U.S. presidential candidate Senator Bernie Sanders smiles during the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Democratic U.S. presidential candidate Senator Bernie Sanders speaks at the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Democratic U.S. presidential candidate Senator Bernie Sanders and former Secretary of State Hillary Clinton discuss an issue at the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young TPX IMAGES OF THE DAY

Democratic U.S. presidential candidate Senator Bernie Sanders and former Secretary of State Hillary Clinton discuss an issue at the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young TPX IMAGES OF THE DAY

Democratic U.S. presidential candidates Senator Bernie Sanders waves as he arrives on stage before of the start of the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Democratic U.S. presidential candidates Senator Bernie Sanders and former Secretary of State Hillary Clinton wave as they arrive on stage before of the start of the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young TPX IMAGES OF THE DAY

Democratic U.S. presidential candidates Senator Bernie Sanders and former Secretary of State Hillary Clinton arrive on stage before of the start of the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Democratic U.S. presidential candidate Senator Bernie Sanders speaks at the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young TPX IMAGES OF THE DAY

Democratic U.S. presidential candidate Senator Bernie Sanders speaks at the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Democratic U.S. presidential candidate Senator Bernie Sanders speaks at the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Democratic U.S. presidential candidate Senator Bernie Sanders speaks as former Secretary of State Hillary Clinton listens at the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Democratic U.S. presidential candidate Senator Bernie Sanders speaks as former Secretary of State Hillary Clinton listens at the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Democratic U.S. presidential candidate Senator Bernie Sanders speaks at the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Democratic U.S. presidential candidate former Secretary of State Hillary Clinton speaks at the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Democratic U.S. presidential candidate former Secretary of State Hillary Clinton speaks at the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Democratic U.S. presidential candidate former Secretary of State Hillary Clinton speaks as Senator Bernie Sanders listens at the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Democratic U.S. presidential candidate Senator Bernie Sanders speaks at the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Democratic U.S. presidential candidate Senator Bernie Sanders speaks at the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Democratic U.S. presidential candidate Senator Bernie Sanders speaks as former Secretary of State Hillary Clinton listens at the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Democratic U.S. presidential candidate former Secretary of State Hillary Clinton speaks as Senator Bernie Sanders listens at the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Democratic U.S. presidential candidate former Secretary of State Hillary Clinton speaks as Senator Bernie Sanders listens at the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Democratic U.S. presidential candidate former Secretary of State Hillary Clinton attends the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Darren Hauck

Democratic U.S. presidential candidate Senator Bernie Sanders attends the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Darren Hauck

Democratic U.S. presidential candidates Senator Bernie Sanders and former Secretary of State Hillary Clinton arrive on stage ahead of the start of the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Darren Hauck

Democratic U.S. presidential candidates Senator Bernie Sanders and former Secretary of State Hillary Clinton arrive on stage ahead of the start of the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Darren Hauck

Democratic U.S. presidential candidates Senator Bernie Sanders and former Secretary of State Hillary Clinton arrive on stage ahead of the start of the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Darren Hauck

Democratic U.S. presidential candidates Senator Bernie Sanders and former Secretary of State Hillary Clinton arrive on stage ahead of the start of the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Darren Hauck

Black Lives Matter supporters protest at the media center across the street from the debate venue ahead of the start of the PBS NewsHour Democratic presidential candidates debate in Milwaukee, Wisconsin, February 11, 2016. REUTERS/Jim Young

Iranian Foreign Minister Mohammad Javad Zarif speaks to the Council on Foreign Relations in New York ahead of next week's United Nations General Assembly September 17, 2014. At right is moderator and journalist Margaret Warner of the Public Broadcasting Service (PBS). REUTERS/Mike Segar (UNITED STATES - Tags: POLITICS MEDIA)

Writer Steven Moffat poses with his Outstanding Writing for a Miniseries, Movie or a Dramatic Special award for the PBS/BBC miniseries "Sherlock" at the 66th Primetime Emmy Awards in Los Angeles, California August 25, 2014. REUTERS/Mike Blake (UNITED STATES -Tags: ENTERTAINMENT)(EMMYS-BACKSTAGE)

Writer Steven Moffat poses with his Outstanding Writing for a Miniseries, Movie or a Dramatic Special award for the PBS/BBC miniseries "Sherlock" at the 66th Primetime Emmy Awards in Los Angeles, California August 25, 2014. REUTERS/Mike Blake (UNITED STATES -Tags: ENTERTAINMENT)(EMMYS-BACKSTAGE)

Writer Steven Moffat poses with his Outstanding Writing for a Miniseries, Movie or a Dramatic Special award for the PBS/BBC miniseries "Sherlock" at the 66th Primetime Emmy Awards in Los Angeles, California August 25, 2014. REUTERS/Mike Blake (UNITED STATES -Tags: ENTERTAINMENT)(EMMYS-BACKSTAGE)

Steven Moffat accepts the award for Outstanding Writing for a Miniseries, Movie or a Dramatic Special for PBS' "Sherlock: His Last Vow"
during the 66th Primetime Emmy Awards in Los Angeles, California August 25, 2014. REUTERS/Mario Anzuoni (UNITED STATES - Tags: ENTERTAINMENT) (EMMYS-SHOW)

Steven Moffat accepts the award for Outstanding Writing for a Miniseries, Movie or a Dramatic Special for PBS "Sherlock: His Last Vow" onstage during the 66th Primetime Emmy Awards in Los Angeles, California August 25, 2014. REUTERS/Mario Anzuoni (UNITED STATES - Tags: Entertainment)(EMMYS-SHOW)

Allison Janney presents the award to Steven Moffat for Outstanding Writing for a Miniseries, Movie or a Dramatic Special for PBS "Sherlock: His Last Vow" onstage during the 66th Primetime Emmy Awards in Los Angeles, California August 25, 2014. REUTERS/Mario Anzuoni (UNITED STATES - Tags: Entertainment)(EMMYS-SHOW)

Michelle Dockery from the PBS/BBC series "Downton Abbey" arrives at the 66th Primetime Emmy Awards in Los Angeles, California August 25, 2014. REUTERS/Lucy Nicholson (UNITED STATES -Tags: ENTERTAINMENT)(EMMYS-ARRIVALS)