code: def line_nbr_from_position(self, y_pos):
          
          editor = self._editor
          height = editor.fontMetrics().height()
          for top, line, block in editor.visible_blocks:
              if top <= y_pos <= top + height:
                  return line
          return -1
docs: Returns the line number from the y_pos.
  
          :param y_pos: Y pos in the editor
          :return: Line number (0 based), -1 if out of range