<s> def guess_format ( filename ) : <EOL> """<STR_LIT>""" <EOL> last_period = filename . rfind ( '<STR_LIT:.>' ) <EOL> if last_period == - <NUM_LIT:1> : <EOL> return '<STR_LIT>' <EOL> extension = filename [ last_period + <NUM_LIT:1> : ] . lower ( ) <EOL> if extension in ( '<STR_LIT>' , '<STR_LIT>' , '<STR_LIT>' , '<STR_LIT>' , '<STR_LIT>' ) : <EOL> return extension <EOL> elif extension in [ '<STR_LIT>' , '<STR_LIT>' ] : <EOL> return '<STR_LIT>' <EOL> return None </s>
