'Provide some completions for dot commands
:param line: The current complete input line
:param token: The word readline is looking for matches
:param beg: Integer offset of token in line
:param end: Integer end of token in line
:return: A list of completions, or an empty list if none'

def complete_command(self, line, token, beg, end):

    if (not self._builtin_commands):
        self._builtin_commands = [('.' + x[len('command_'):]) for x in dir(self) if (x.startswith('command_') and (x != 'command_headers'))]
    if (beg == 0):
        return [(x + '    ') for x in self._builtin_commands if x.startswith(token)]
    return None
