docs: def __get_constants(self):
          """
          Gets the constants from the class that acts like a namespace for constants and adds them to the replace pairs.
          """
          helper = ConstantClass(self._constants_class_name, self._io)
          helper.reload()
          constants = helper.constants()
  
          for name, value in constants.items():
              self._add_replace_pair(name, value, True)
  
          self._io.text('Read {0} constants for substitution from <fso>{1}</fso>'.
                        format(len(constants), helper.file_name()))