def METHOD_NAME(self, a, b):
    """ Given two Triangles with mismatched indices, this method aligns
        their indices """
    if len(a) == 1 and len(b) == 1:
        return a, b
    METHOD_NAME = list(set(a.key_labels).METHOD_NAME(set(b.key_labels)))
    if METHOD_NAME == []:
        return a, b
    a_idx = a.index[METHOD_NAME]
    b_idx = b.index[METHOD_NAME]
    idx_intersection = list(
        set(a_idx.set_index(METHOD_NAME).index.METHOD_NAME(
            b_idx.set_index(METHOD_NAME).index)))
    if (len(a) == 1 or len(b) == 1) and idx_intersection == []:
        return a, b
    b = b.iloc[b_idx[b_idx[METHOD_NAME].set_index(METHOD_NAME).index.isin(idx_intersection)].index]
    a = a.iloc[a_idx[a_idx[METHOD_NAME].set_index(METHOD_NAME).index.isin(idx_intersection)].index]
    return a, b