'Mapping from _view_of object --> view column. Returns a
single item dict {column name:column value} or list of dicts.'

@classmethod
def _obj_to_column(cls, objs):

    (objs, is_single) = tup(objs, ret_is_single=True)
    columns = [{obj._id: obj._id} for obj in objs]
    if (len(columns) == 1):
        return columns[0]
    else:
        return columns
