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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 shell_out(cmd, timeout=30, chroot=None, runat=None):
 """Shell out to an external command and return the output or the empty string in case of error. """

    return sos_get_command_output(cmd, timeout=timeout,
                                  chroot=chroot, chdir=runat)['output']