user: Question: Who directed the episode that had 0.54 million U.S. viewers? 
Columns: ['No.', '#', 'Title', 'Directed by', 'Story by', 'Teleplay by', 'Original air date', 'U.S. viewers (millions)']
Types: ['real', 'real', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: [22.0, 1.0, '"Knock with Me – Rock with Me"', 'Anthony Hemingway', 'David Simon & Anthony Bourdain', 'David Simon', 'September23,2012', '0.57']
SQL:

assistant: SELECT "Directed by" FROM "Table" WHERE "U.S. viewers (millions)" = '0.54';