code: def add_pin_at_xy(self, x, y, text, location='above right',
                        relative_position=.9, use_arrow=True, style=None):
          
          if relative_position is None:
              if location == 'left':
                  relative_position = 0.
              elif location == 'right':
                  relative_position = 1.
              else:
                  relative_position = .8
  
          x, y = self._calc_position_for_pin(x, y, relative_position)
          self.pin_list.append({'x': x, 'y': y, 'text': text,
                                'location': location,
                                'use_arrow': use_arrow,
                                'options': style})
docs: Add pin at x, y location.
  
          :param x: array, list or float, specifying the location of the
              pin.
          :param y: array, list or float, specifying the location of the
              pin.
          :param text: the text of the pin label.
          :param location: the location of the pin relative to the data
              point.  Any location accepted by TikZ is allowed.
          :param relative_position: location of the data point as a relative
              number between 0 and 1.
          :param use_arrow: specifies whether to draw an arrow between the
              data point and the pin label text.
          :type use_arrow: boolean
          :param style: optional TikZ styles to apply (e.g. 'red').
  
          If x, y are arrays or lists, relative position is used to pick a
          point from the arrays.  A relative position of 0.0 will be the
          first point from the series, while 1.0 will be the last point.