docs: def region_by_identifier(self, identifier):
          """Return region of interest corresponding to the supplied identifier.
  
          :param identifier: integer corresponding to the segment of interest
          :returns: `jicbioimage.core.region.Region`
          """
  
          if identifier < 0:
              raise(ValueError("Identifier must be a positive integer."))
  
          if not np.equal(np.mod(identifier, 1), 0):
              raise(ValueError("Identifier must be a positive integer."))
  
          if identifier == 0:
              raise(ValueError("0 represents the background."))
  
          return Region.select_from_array(self, identifier)