code: def exec(self, *command_tokens, **command_env):
  		
  		mutated_command_tokens = self.mutate_command_tokens(*command_tokens)
  		if mutated_command_tokens is not None:
  			command = self.selector().select(*mutated_command_tokens, **command_env)
  			if command is not None:
  				return command.exec(*mutated_command_tokens, **command_env)
  
  		raise RuntimeError('Command mismatch: %s' % self.join_tokens(*command_tokens))
docs: :meth:`.WCommandProto.exec` implementation