'Set the formatter to use for the major tick labels.
Parameters
formatter : str or Formatter
The format or formatter to use.'

def set_major_formatter(self, formatter):

    if isinstance(formatter, Formatter):
        raise NotImplementedError()
    elif isinstance(formatter, six.string_types):
        self._formatter_locator.format = formatter
    else:
        raise TypeError('formatter    should    be    a    string    or    a    Formatter    instance')
