'Returns list of (pk, object) nice to use on select2.
Use only for related columns.
Always filters with add_form_query_rel_fields, and accepts extra filters
on endpoint arguments.
:param col_name: The related column name
:return: JSON response'

@expose_api(name='column_add', url='/api/column/add/<col_name>', methods=['GET'])
@has_access_api
@permission_name('add')
def api_column_add(self, col_name):

    filter_rel_fields = None
    if self.add_form_query_rel_fields:
        filter_rel_fields = self.add_form_query_rel_fields.get(col_name)
    ret_json = self._get_related_column_data(col_name, filter_rel_fields)
    response = make_response(ret_json, 200)
    response.headers['Content-Type'] = 'application/json'
    return response
