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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def _execute_command(cmd, at_time=None):
    '''
    Helper function to execute the command

    :param str cmd: the command to run

    :param str at_time: If passed, the cmd will be scheduled.

    Returns: bool
    '''
    if at_time:
        cmd = 'echo \'{0}\' | at {1}'.format(cmd, _cmd_quote(at_time))
    return not bool(__salt__['cmd.retcode'](cmd, python_shell=True))