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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 required_from_env(key):
 """ Retrieve a required variable from the current environment variables. Raises a ValueError if the env variable is not found or has no value. """

    val = os.environ.get(key)
    if not val:
        raise ValueError(
            "Required argument '{}' not supplied and not found in environment variables".format(key))
    return val