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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 conf_merger(user_dict, variable):
 """ Merge global configuration with user's personal configuration. Global configuration has always higher priority. """

    if variable not in globals().keys():
        raise NameError("Unknown variable '%s'." % variable)

    if variable not in user_dict:
        return globals()[variable]

    return globals()[variable] and user_dict[variable]