def __radd__(self, other):
        if is_list_like(other):
            warnings.warn("using '+' to provide set union with Indexes is "
                          "deprecated, use '|' or .union()", FutureWarning,
                          stacklevel=2)
        return Index(other + np.array(self))
dataset/ETHPy150Open pydata/pandas/pandas/indexes/base.py/Index.__radd__/original