docs: def set_label(self, row, column, text, location='upper right',
                    style=None):
          """Set a label for the subplot.
  
          :param row,column: specify the subplot.
          :param text: the label text.
          :param location: the location of the label inside the plot.  May
              be one of 'center', 'upper right', 'lower right', 'upper
              left', 'lower left'.
          :param style: any TikZ style to style the text.
  
          """
          subplot = self.get_subplot_at(row, column)
          subplot.set_label(text, location, style)