Returns VpcConfig dict either from this Estimator's subnets and security groups,
        or else validate and return an optional override value.

def get_vpc_config(self, vpc_config_override=vpc_utils.VPC_CONFIG_DEFAULT):
        """
        Returns VpcConfig dict either from this Estimator's subnets and security groups,
        or else validate and return an optional override value.
        """
        if vpc_config_override is vpc_utils.VPC_CONFIG_DEFAULT:
            return vpc_utils.to_dict(self.subnets, self.security_group_ids)
        else:
            return vpc_utils.sanitize(vpc_config_override)