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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 _check_env_var(envvar: str) -> bool: """Check Environment Variable to verify that it is set and not empty. :param envvar: Environment Variable to Check. :returns: True if Environment Variable is set and not empty. :raises: KeyError if Environment Variable is not set or is empty. .. versionadded:: 0.0.12 """

    if os.getenv(envvar) is None:
        raise KeyError(
            "Required ENVVAR: {0} is not set".format(envvar))
    if not os.getenv(envvar):  # test if env var is empty
        raise KeyError(
            "Required ENVVAR: {0} is empty".format(envvar))
    return True