docs: def __read_source_file(self):
          """
          Reads the file with the source of the stored routine.
          """
          with open(self._source_filename, 'r', encoding=self._routine_file_encoding) as file:
              self._routine_source_code = file.read()
  
          self._routine_source_code_lines = self._routine_source_code.split("\n")