code: def _make_dataset(cls, coords):
          
          class Slice(cls._SliceType):
              extra_coords = coords
  
          Slice.__name__ = '%s.slice(%s)' % (
              cls.__name__,
              ', '.join('%s=%r' % item for item in coords.items()),
          )
          return Slice
docs: Construct a new dataset given the coordinates.