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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 index_of(self, item):
 """ Returns the first index of specified items's occurrences in this list. If specified item is not present in this list, returns -1. :param item: (object), the specified item to be searched for. :return: (int), the first index of specified items's occurrences, -1 if item is not present in this list. """

        check_not_none(item, "Value can't be None")
        item_data = self._to_data(item)
        return self._encode_invoke(list_index_of_codec, value=item_data)