What year was incumbent william f. stevenson first elected?
{'header': ['District', 'Incumbent', 'Party', 'First elected', 'Result', 'Candidates'], 'page_title': 'United States House of Representatives elections, 1920', 'section_title': '', 'caption': '', 'rows': [['South Carolina 1', 'Richard S. Whaley', 'Democratic', '1913', 'Retired Democratic hold', 'W. Turner Logan (D) 92.6% ? Saspartas (I) 7.4%'], ['South Carolina 2', 'James F. Byrnes', 'Democratic', '1910', 'Re-elected', 'James F. Byrnes (D) Unopposed'], ['South Carolina 3', 'Frederick H. Dominick', 'Democratic', '1916', 'Re-elected', 'Frederick H. Dominick (D) Unopposed'], ['South Carolina 4', 'Samuel J. Nicholls', 'Democratic', '1915', 'Retired Democratic hold', 'John J. McSwain (D) Unopposed'], ['South Carolina 5', 'William F. Stevenson', 'Democratic', '1917', 'Re-elected', 'William F. Stevenson (D) Unopposed'], ['South Carolina 6', 'Philip H. Stoll', 'Democratic', '1919', 'Re-elected', 'Philip H. Stoll (D) Unopposed']]}