Return a dictionary for the class fields description.
        Fields should NOT be wrapped by _precomputed_field, if necessary

def _describe_fields(cls):
        """
        Return a dictionary for the class fields description.
        Fields should NOT be wrapped by _precomputed_field, if necessary
        """
        dispatch_table = {
            'ShortestPathModel': 'sssp',
            'GraphColoringModel': 'graph_coloring',
            'PagerankModel': 'pagerank',
            'ConnectedComponentsModel': 'connected_components',
            'TriangleCountingModel': 'triangle_counting',
            'KcoreModel': 'kcore',
            'DegreeCountingModel': 'degree_count',
            'LabelPropagationModel': 'label_propagation'
        }
        try:
            toolkit_name = dispatch_table[cls.__name__]
            toolkit = _tc.extensions._toolkits.graph.__dict__[toolkit_name]
            return toolkit.get_model_fields({})
        except:
            raise RuntimeError('Model %s does not have fields description' % cls.__name__)