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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 icon_cache_key(method, self, brain_or_object):
 """Generates a cache key for the icon lookup Includes the virtual URL to handle multiple HTTP/HTTPS domains Example: http://senaite.local/clients?modified=1512033263370 """

    url = api.get_url(brain_or_object)
    modified = api.get_modification_date(brain_or_object).millis()
    key = "{}?modified={}".format(url, modified)
    logger.debug("Generated Cache Key: {}".format(key))
    return key