docs: def title(self, title=None):
          """Returns or sets (if a value is provided) the chart's title.
  
          :param str title: If given, the chart's title will be set to this.
          :rtype: ``str``"""
  
          if title is None:
              return self._title
          else:
              if not isinstance(title, str):
                  raise TypeError("title must be str, not '%s'" % str(title))
              self._title = title