Append the ``element`` to the ``field`` of the record.

        This method is smart: it does nothing if ``element`` is empty and
        creates ``field`` if it does not exit yet.

        Args:
            :param field: the name of the field of the record to append to
            :type field: string
            :param element: the element to append

def _append_to(self, field, element):
        """Append the ``element`` to the ``field`` of the record.

        This method is smart: it does nothing if ``element`` is empty and
        creates ``field`` if it does not exit yet.

        Args:
            :param field: the name of the field of the record to append to
            :type field: string
            :param element: the element to append
        """
        if element not in EMPTIES:
            self.obj.setdefault(field, [])
            self.obj.get(field).append(element)