code: def set_delimiter(self, delimiter):
          
          for key in self.keys():
              if delimiter in key:
                  raise ValueError('Key {!r} collides with delimiter {!r}', key,
                                   delimiter)
          self._delimiter = delimiter
          for key in self._values.keys():
              if isinstance(self._values[key], FlatDict):
                  self._values[key].set_delimiter(delimiter)
docs: Override the default or passed in delimiter with a new value. If
          the requested delimiter already exists in a key, a :exc:`ValueError`
          will be raised.
  
          :param str delimiter: The delimiter to use
          :raises: ValueError