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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 make_user_agent_string(component=None):
 """ Return a nice and uniform user-agent string to be used when Invenio act as a client in HTTP requests. """

    ret = "Invenio-%s (+%s; \"%s\")" % (cfg.get('CFG_VERSION'),
                                        cfg.get('CFG_SITE_URL'), cfg.get('CFG_SITE_NAME'))
    if component:
        ret += " %s" % component
    return ret