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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 _indexes(self):
 """Instantiate the indexes only when asked Returns ------- list An empty list if the field is not indexable, else a list of all indexes tied to the field. If no indexes where passed when creating the field, the default indexes from the field/model/database will be used. If still no index classes, it will raise Raises ------ ImplementationError If no index classes available for this field """

        if not self.indexable:
            return []
        if not self.index_classes:
            self.index_classes = self.get_default_indexes()[::1]
        if not self.index_classes:
            raise ImplementationError('%s field is indexable but has no indexes attached' %
                                      self.__class__.__name__)

        return [index_class(field=self) for index_class in self.index_classes]