code: def unpack_scalar(cls, dataset, data):
          
          if np.isscalar(data) or len(data) != 1:
              return data
          key = list(data.keys())[0]
  
          if len(data[key]) == 1 and key in dataset.vdims:
              return data[key][0]
docs: Given a dataset object and data in the appropriate format for
          the interface, return a simple scalar.