code: def add_field_like(self, name, like_array):
          
          new_shape = list(like_array.shape)
          new_shape[0] = len(self)
          new_data = ma.empty(new_shape, like_array.dtype)
          new_data.mask = True
          self.add_field(name, new_data)
docs: Add a new field to the Datamat with the dtype of the
          like_array and the shape of the like_array except for the first
          dimension which will be instead the field-length of this Datamat.