def _derive_typedef(typ):
    '''Return single, existing super type typedef or None.
    '''
    v = [v for v in _values(_typedefs) if _issubclass(typ, v.type)]
    if len(v) == 1:
        return v[0]
    return None
Return single, existing super type typedef or None.
    
recipes/Python/546530_Size_of_Python_objects_revised/recipe-546530.py