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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 set(self, alias, options, target=None):
 """ Add an alias. :param alias: The name of the alias to add. :param options: The easy-thumbnails options dictonary for this alias (should include ``size``). :param target: A field, model, or app to limit this alias to (optional). """

        target = self._coerce_target(target) or ''
        target_aliases = self._aliases.setdefault(target, {})
        target_aliases[alias] = options