code: def _apply(self, input_string):
          
          e = self.editor
  
          # Parse command.
          m = COMMAND_GRAMMAR.match(input_string)
          if m is None:
              return
  
          variables = m.variables()
  
          command = variables.get('command')
          set_option = variables.get('set_option')
  
          # Preview colorschemes.
          if command == 'colorscheme':
              colorscheme = variables.get('colorscheme')
              if colorscheme:
                  e.use_colorscheme(colorscheme)
  
          # Preview some set commands.
          if command == 'set':
              if set_option in ('hlsearch', 'hls'):
                  e.highlight_search = True
              elif set_option in ('nohlsearch', 'nohls'):
                  e.highlight_search = False
              elif set_option in ('nu', 'number'):
                  e.show_line_numbers = True
              elif set_option in ('nonu', 'nonumber'):
                  e.show_line_numbers = False
              elif set_option in ('ruler', 'ru'):
                  e.show_ruler = True
              elif set_option in ('noruler', 'noru'):
                  e.show_ruler = False
              elif set_option in ('relativenumber', 'rnu'):
                  e.relative_number = True
              elif set_option in ('norelativenumber', 'nornu'):
                  e.relative_number = False
              elif set_option in ('cursorline', 'cul'):
                  e.cursorline = True
              elif set_option in ('cursorcolumn', 'cuc'):
                  e.cursorcolumn = True
              elif set_option in ('nocursorline', 'nocul'):
                  e.cursorline = False
              elif set_option in ('nocursorcolumn', 'nocuc'):
                  e.cursorcolumn = False
              elif set_option in ('colorcolumn', 'cc'):
                  value = variables.get('set_value', '')
                  if value:
                      e.colorcolumn = [
                          int(v) for v in value.split(',') if v.isdigit()]
docs: Apply command.