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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 check_output(args, env=None, sp=subprocess):
 """Call an external binary and return its stdout."""

    log.debug('calling %s with env %s', args, env)
    output = sp.check_output(args=args, env=env)
    log.debug('output: %r', output)
    return output