code: def get_height_for_line(self, lineno, width):
          
          try:
              return self._line_heights[lineno, width]
          except KeyError:
              text = token_list_to_text(self.get_line(lineno))
              result = self.get_height_for_text(text, width)
  
              # Cache and return
              self._line_heights[lineno, width] = result
              return result
docs: Return the height that a given line would need if it is rendered in a
          space with the given width.