def append(self, other):
        to_concat, name = self._ensure_compat_append(other)
        attribs = self._get_attributes_dict()
        attribs['name'] = name
        return self._shallow_copy_with_infer(
            np.concatenate(to_concat), **attribs)
Append a collection of Index options together
dataset/ETHPy150Open pydata/pandas/pandas/indexes/base.py/Index.append