def METHOD_NAME(self, params, shape, errors, name):
    # our parser sets the value of required members to None if they are not in the incoming request. we correct
    # this behavior here to get the correct error messages.
    for required_member in shape.metadata.get("required", []):
        if required_member in params and params[required_member] is None:
            params.pop(required_member)
    super(ParamValidator, self).METHOD_NAME(params, shape, errors, name)