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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 call(cmd, shell=True, cwd=None, universal_newlines=True, stderr=STDOUT):
 """Just execute a specific command."""

        return Shell._run(call, cmd, shell=shell, cwd=cwd, stderr=stderr,
                          universal_newlines=universal_newlines)