<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def execute(cur, sql):
 """Execute a special command and return the results. If the special command is not supported a KeyError will be raised. """

    command, verbose, arg = parse_special_command(sql)

    if (command not in COMMANDS) and (command.lower() not in COMMANDS):
        raise CommandNotFound

    try:
        special_cmd = COMMANDS[command]
    except KeyError:
        special_cmd = COMMANDS[command.lower()]
        if special_cmd.case_sensitive:
            raise CommandNotFound('Command not found: %s' % command)

    # "help <SQL KEYWORD> is a special case.
    if command == 'help' and arg:
        return show_keyword_help(cur=cur, arg=arg)

    if special_cmd.arg_type == NO_QUERY:
        return special_cmd.handler()
    elif special_cmd.arg_type == PARSED_QUERY:
        return special_cmd.handler(cur=cur, arg=arg, verbose=verbose)
    elif special_cmd.arg_type == RAW_QUERY:
        return special_cmd.handler(cur=cur, query=sql)