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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 main():

 """Cli entrypoint.
 """

    if len(sys.argv) == 2:
        fname = sys.argv[1]
        data = json.load(open(fname, 'rb'))
    else:
        data = json.loads(sys.stdin.read())
    print(pydeps2reqs(data))