def add_at(self, index, item):
check_not_none(item, "<STR_LIT>")<EOL>element_data = self._to_data(item)<EOL>return self._encode_invoke(list_add_with_index_codec, index=index, value=element_data)<EOL>
Adds the specified item at the specific position in this list. Element in this position and following elements
are shifted to the right, if any.

:param index: (int), the specified index to insert the item.
:param item: (object), the specified item to be inserted.