def filter_duplicate_key(line, message, line_number, marked_line_numbers,<EOL>source, previous_line='<STR_LIT>'):
if marked_line_numbers and line_number == sorted(marked_line_numbers)[<NUM_LIT:0>]:<EOL><INDENT>return '<STR_LIT>'<EOL><DEDENT>return line<EOL>
Return '' if first occurrence of the key otherwise return `line`.