<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def extract_code_from_function(function):
 """Return code handled by function."""

    if not function.__name__.startswith('fix_'):
        return None

    code = re.sub('^fix_', '', function.__name__)
    if not code:
        return None

    try:
        int(code[1:])
    except ValueError:
        return None

    return code