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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 _git_command(params, cwd):
 """ Executes a git command, returning the output :param params: A list of the parameters to pass to git :param cwd: The working directory to execute git in :return: A 2-element tuple of (stdout, stderr) """


    proc = subprocess.Popen(
        ['git'] + params,
        stdout=subprocess.PIPE,
        stderr=subprocess.STDOUT,
        cwd=cwd
    )
    stdout, stderr = proc.communicate()
    code = proc.wait()
    if code != 0:
        e = OSError('git exit code was non-zero')
        e.stdout = stdout
        raise e
    return stdout.decode('utf-8').strip()