What is the maximum season # with a u.s. air date is may 1, 2009
{'header': ['Season #', 'Series #', 'Title', 'Canadian airdate', 'U.S. airdate', 'Production code'], 'page_title': '', 'section_title': '', 'caption': '', 'rows': [['1', '14', '"Dangerous Liaisons"', 'April 21, 2009', 'April 3, 2009', '201'], ['2', '15', '"Documentary"', 'April 27, 2009', 'April 10, 2009', '202'], ['3', '16', '"Dermabrasion"', 'May 4, 2009', 'April 17, 2009', '203'], ['4', '17', '"Different Hearts"', 'May 11, 2009', 'April 24, 2009', '204'], ['5', '18', '"Destiny"', 'May 18, 2009', 'May 1, 2009', '205'], ['6', '19', '"Duluth, Minnesota"', 'May 25, 2009', 'May 8, 2009', '206'], ['7', '20', '"Debtor\'s Prison"', 'June 1, 2009', 'May 15, 2009', '207']]}