code: def add_empty_dataset(self, value=1):
          
          subdata = np.ones(self.grid.nr_of_elements) * value
          pid = self.add_data(subdata)
          return pid
docs: Create an empty data set. Empty means: all elements have the same
          value.
  
          Parameters
          ----------
          value: float, optional
              which value to assign all element parameters. Default is one.