@classmethod
def clean_resources(cls, resources, request=None, **kwargs):
    """ Clean resources before models management.

        If models management requires resources, such as database calls or
        external services communication, one may possible to clean resources
        before it.
        It is also possible to validate user permissions to do operation. Use
        form validation if validation does not require user access and Resource
        validation (this method) if it requires to access user object.

        Parameters
        ----------
        resources : list
            List of dictionaries - serialized objects.

        Returns
        -------
        resources : list
            List of cleaned resources

        Raises
        ------
        django.forms.ValidationError in case of validation errors

        """
    return resources
