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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 env(var_name, default=False):
 """ Get the environment variable or assume a default, but let the user know about the error."""

    try:
        value = os.environ[var_name]
        if str(value).strip().lower() in ['false', 'no', 'off' '0', 'none', 'null']:
            return None
        return value
    except:
        from traceback import format_exc
        msg = format_exc() + '\n' + "Unable to find the %s environment variable.\nUsing the value %s (the default) instead.\n" % (var_name, default)
        warnings.warn(msg)
        return default