code: def display_help(self):
          
          helptxt = ["h : Toggle help",
                     "A/a, B/b or C/c : Increase/decrease cell by one a,"
                     " b or c unit vector", "# : Toggle showing of polyhedrons",
                     "-: Toggle showing of bonds", "r : Reset camera direction",
                     "[/]: Decrease or increase poly_radii_tol_factor "
                     "by 0.05. Value = " + str(self.poly_radii_tol_factor),
                     "Up/Down: Rotate view along Up direction by 90 "
                     "clockwise/anticlockwise",
                     "Left/right: Rotate view along camera direction by "
                     "90 clockwise/anticlockwise", "s: Save view to image.png",
                     "o: Orthogonalize structure"]
          self.helptxt_mapper.SetInput("\n".join(helptxt))
          self.helptxt_actor.SetPosition(10, 10)
          self.helptxt_actor.VisibilityOn()
docs: Display the help for various keyboard shortcuts.