def src(filename):
if filename is None:<EOL><INDENT>return filename<EOL><DEDENT>if sys.platform.startswith('<STR_LIT>') and filename.endswith('<STR_LIT>'):<EOL><INDENT>return '<STR_LIT:.>'.join((filename[:-<NUM_LIT:9>], '<STR_LIT>'))<EOL><DEDENT>base, ext = os.path.splitext(filename)<EOL>if ext in ('<STR_LIT>', '<STR_LIT>', '<STR_LIT>'):<EOL><INDENT>return '<STR_LIT:.>'.join((base, '<STR_LIT>'))<EOL><DEDENT>return filename<EOL>
Find the python source file for a .pyc, .pyo or $py.class file on
    jython. Returns the filename provided if it is not a python source
    file.