Former first lady Michelle Obama attends the Girls Opportunity Alliance program with Room to Read at the Can Giuoc Highschool in Long An province, Vietnam, December 9, 2019.

Former U.S. President Barack Obama walks past a portrait of former first lady Michelle Obama during an unveiling ceremony at the Smithsonian’s National Portrait Gallery in Washington, U.S., February 12, 2018.

Canada's Prime Minister Justin Trudeau speaks with former United States President Barack Obama at a restaurant during Obama's visit to address the Montreal Chamber of Commerce, in Montreal, Quebec, Canada June 6, 2017. Picture taken June 6, 2017. Prime Minister's Office/Handout via REUTERS

Attendees react as former president Barack Obama greets supporters after joining New Jersey Democratic Gubernatorial candidate Jim Murphy at a rally in Newark, New Jersey, U.S. October 19, 2017.

Five former U.S. presidents, Jimmy Carter, George H.W. Bush, Barack Obama, George W. Bush and Bill Clinton, speak during a concert at Texas A&M University benefiting hurricane relief efforts in College Station, Texas, U.S., October 21, 2017.

Former U.S. President Barack Obama speaks at the memorial service of U.S. Senator John McCain (R-AZ) at National Cathedral in Washington, U.S., September 1, 2018.

Former U.S. President Barack Obama speaks during funeral services for late U.S. Rep. Elijah Cummings (D-MD) at the New Psalmist Baptist Church in Baltimore, Maryland, U.S., October 25, 2019. Justin T. Gellerson/Pool via REUTERS

Former U.S. President Barack Obama participates in a political rally for California Democratic candidates during a event in Anaheim, California, U.S., September 8, 2018. Left to right are candidates Josh Harder (CA-10), TJ Cox (CA-21), Gil Cisneros (CA-39), Katie Porter (CA-45), Harley Rouda (CA-48) and Mike Levin (CA-49).

Former U.S. President Barack Obama reacts as he addresses players at the basketball court during the launch of Sauti Kuu resource centre near his ancestral home in Nyangoma Kogelo village in Siaya county, western Kenya July 16, 2018.

US President Barack Obama and NBA commissioner Adam Silver before game two of the 2019 NBA Finals between the Golden State Warriors and the Toronto Raptors at Scotiabank Arena. Mandatory Credit: Dan Hamilton-USA TODAY Sports

Former First Lady Michelle Obama speaks during the second day of the first Obama Foundation Summit in Chicago, Illinois, U.S. November 1, 2017.

Former U.S. Presidents (from Left) Barack Obama and George W. Bush and Bill Clinton smile during the first round foursomes match of The President's Cup golf tournament at Liberty National Golf Course. Mandatory Credit: Bill Streicher-USA TODAY Sports

Former U.S. President Barack Obama reacts during a community service project in Petaling Jaya, Malaysia, December 12, 2019.

U.S. President Donald Trump, first lady Melania Trump, former President Barack Obama, former first lady Michelle Obama, former President Bill Clinton, former Secretary of State Hillary Clinton, former President Jimmy Carter and former first lady Rosalynn Carter participate in the State Funeral for former President George H.W. Bush, at the National Cathedral, Wednesday, Dec. 5, 2018 in Washington. Alex Brandon/Pool via REUTERS

61st Grammy Awards - Show - Los Angeles, California, U.S., February 10, 2019 - Lady Gaga, Jennifer Lopez, Alicia Keys, former first lady Michelle Obama and Jada Pinkett Smith.

Oprah Winfrey talks with former first lady Michelle Obama as she begins her Becoming book tour with a stop at the United Center in Chicago, Illinois, U.S., November 13, 2018.

Britain's Prince Harry (R) and former U.S. President Barack Obama watch a wheelchair basketball event during the Invictus Games in Toronto, Ontario, Canada September 29, 2017.

Former U.S. President Barack Obama waves while walking with his daughter Mali and his wife Michelle during a visit to the 9th-century Borobudur Temple in Magelang, Indonesia June 28, 2017.

Former United States President Barack Obama (2nd L), his wife Michelle (3rd L) along with his daughters Sasha (C) and Malia (2nd R) go rafting while on holiday in Bongkasa Village, Badung Regency, Bali, Indonesia June 26, 2017 in this photo taken by Antara Foto. Antara Foto/Wira Suryantala/ via REUTERS

Former first lady Michelle Obama smiles as she begins her book tour with a stop at the Whitney M. Young Magnet High School in Chicago, Illinois, U.S., November 12, 2018.

Former U.S. President Barack Obama visits Prambanan Temple in Sleman, Yogyakarta, Indonesia June 29, 2017 in this photo taken by Antara Foto. Antara Foto/Andreas Fitri Atmoko/ via REUTERS.

Former first lady Michelle Obama speaks at the AccorHotels Arena during a book tour to promote her memoir "Becoming" in Paris, France, April 16, 2019.

Former U.S. President Barack Obama and former first lady Michelle Obama hold hands between their portraits during an unveiling ceremony at the Smithsonian’s National Portrait Gallery in Washington, U.S., February 12, 2018.

Canada's Prime Minister Justin Trudeau and former U.S. President Barack Obama meet at Big Rig brewery in Kanata, Ontario, Canada May 31, 2019. Obama later spoke to an audience of about 12,000 people at an event hosted by the progressive think-tank Canada 2020. Picture taken May 31, 2019. Adam Scott/Prime Minister's Office/Handout via REUTERS.