code: def bind_key(pymux, variables):
      
      key = variables['<key>']
      command = variables['<command>']
      arguments = variables['<arguments>']
      needs_prefix = not variables['-n']
  
      try:
          pymux.key_bindings_manager.add_custom_binding(
              key, command, arguments, needs_prefix=needs_prefix)
      except ValueError:
          raise CommandException('Invalid key: %r' % (key, ))
docs: Bind a key sequence.
      -n: Not necessary to use the prefix.