def _execute(self, func, command, **new_attributes):
        """
        Execute command.
        """
        if self._cfg_factory:
            # if we have a cfg_factory
            try:
                # we try to load a config with the factory
                if self.cfg_file:
                    self.cfg = self._cfg_factory(self.cfg_file)
            except Exception as error:
                # raise se exception
                self._cfg_error(error)
        # let's get command(function) argspec
        arg_specs = inspect.getargspec(command)
        if arg_specs.defaults:
            # if we have defaults
            # count defaults arguments
            count = len(arg_specs.defaults)
            # get arguments names
            args_names = arg_specs.args[:count]
            # get keyword arguments names
            kwargs_name = arg_specs.args[count:]
        else:
            # else all names are the args only
            args_names = arg_specs.args
            # and keyword arguments is empty
            kwargs_name = []
        pargs = []
        kwargs = {}
        # for every argument in argument names
        for name in args_names:
            if name == 'args':
                # if argument name is *special name* **args**
                # we append a reference to self.args
                pargs.append(self.args)
            elif name == 'self':
                # else if argment name is *special name* **self**
                if ArgParseInated in inspect.getmro(func.__cls__):
                    # if the class that holds the function is subclass of
                    # ArgParseInated we'll instantiate it, passing some
                    # parameter
                    pargs.append(func.__cls__(self, **new_attributes))
                else:
                    # else we'll instatiate the class without parameters
                    pargs.append(func.__cls__())
            else:
                # else we'll append the argument getting it from the self.args
                pargs.append(getattr(self.args, name))
        # for every argument in keyword arguments
        for name in kwargs_name:
            if name == 'args':
                # if argument name is *special name* **args**
                # we set for the arg a reference to self.args
                kwargs[name] = self.args
            elif name in self.args:
                # else if name is in self.args we'll set the relative value.
                kwargs[name] = getattr(self.args, name)
        # set the **global** write function
        setattr(__builtin__, self._write_name, self.write)
        # set the **global** write line function
        setattr(__builtin__, self._write_line_name, self.writeln)
        # let's setup something.
        for setup_func in self.setup:
            setup_func(self)
        # call event before_execute
        self._self_event('before_execute', command, *pargs, **kwargs)
        # if events returns a non None value we use it as retrval.
        retval, pargs, kwargs = self._call_event(
            'before_execute', command, pargs, kwargs)
        # if before_execute event returns None go on with command
        if retval is None:
            # let's execute the command and assign the returned value to retval
            retval = command(*pargs, **kwargs)
            # call event after_execute
            self._call_event('after_execute', command, pargs, kwargs)
            self._self_event('after_execute', command, *pargs, **kwargs)
        if self.auto_exit:
            # if we have auto_exit is True
            if retval is None:
                self._self_event(
                    'before_exit_ok', command, retval=EXIT_OK, *pargs, **kwargs)
                # if retval is None we'll assume it's EXIT_OK
                self.exit(EXIT_OK)
            elif isinstance(retval, basestring):
                self._self_event('before_exit_ok', command, retval=retval, *pargs, **kwargs)
                # else if retval is a string we will exit with the message and
                # ERRORCODE is equal to 0
                self.exit(EXIT_OK, retval)
            elif isinstance(retval, int):
                if retval == EXIT_OK:
                    self._self_event('before_exit_ok', command, retval=retval, *pargs, **kwargs)
                else:
                    self._self_event('before_exit_error', command, retval=retval, *pargs, **kwargs)
                # else if retval is an integer we'll exits with it as ERRORCODE
                self.exit(retval)
            elif isinstance(retval, (tuple, list,)):
                self._self_event('before_exit_error', command, retval=retval, *pargs, **kwargs)
                # if retval is a tuple or a list we'll exist with ERRORCODE and
                # message
                self.exit(retval[0], retval[1])
            self._self_event('before_exit', command, retval=retval, *pargs, **kwargs)
            self.exit()
        else:
            # else if auto_exit is not True
            # we'll simply return  retval
            return retval
Execute command.