def resolve_attr(attr_name, dct, mro):
    """ Resolve an attribute from a MRO

        If the attribute is not present anywhere, None is returned
        Parameters:
            attr_name: The name of the attribte to resolve
            dct: The dictionary of the most derived class body
            mro: The C3 linearised list of bases
    """
    try:
        return dct[attr_name]
    except KeyError:
        pass
    for base in mro:
        try:
            return base.__dict__[attr_name]
        except KeyError:
            pass