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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 ensure_environment(variables):
 """ Check os.environ to ensure that a given collection of variables has been set. :param variables: A collection of environment variable names :returns: os.environ :raises IncompleteEnvironment: if any variables are not set, with the exception's ``variables`` attribute populated with the missing variables """

    missing = [v for v in variables if v not in os.environ]
    if missing:
        formatted = ', '.join(missing)
        message = 'Environment variables not set: {}'.format(formatted)
        raise IncompleteEnvironment(message, missing)
    return os.environ