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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 cwd():
 """Return the be current working directory"""

    cwd = os.environ.get("BE_CWD")
    if cwd and not os.path.isdir(cwd):
        sys.stderr.write("ERROR: %s is not a directory" % cwd)
        sys.exit(lib.USER_ERROR)
    return cwd or os.getcwd().replace("\\", "/")