def _get_valid_file_types():
 return ', '.join([', '.join(IMAGE_TYPES[ft].extensions) for ft in IMAGE_TYPES.keys()])

def _get_valid_file_types ( ) : return ', ' . join ( [ ', ' . join ( IMAGE_TYPES [ ft ] . extensions ) for ft in IMAGE_TYPES . keys ( ) ] )
return comma separated string of valid file types .