'Render/process the form. To be implemented in subclass.
@param request: the S3Request
@param resource: the target S3Resource
@param record_id: the record ID
@param readonly: render the form read-only
@param message: message upon successful form submission
@param format: data format extension (for audit)
@param options: keyword options for the form
@return: a FORM instance'

def __call__(self, request=None, resource=None, record_id=None, readonly=False, message='Record    created/updated', format=None, **options):

    return None
