def _argmax(V: npt.NDArray) -> tuple[int, float]:
    """Returns a tuple (index of max number, max number)."""
    V = (V * V.conj()).real
    idx_max = np.argmax(V)
    V[idx_max] = 0
    return cast(int, idx_max), np.max(V)
Returns a tuple (index of max number, max number).
cirq-core/cirq/transformers/analytical_decompositions/pauli_string_decomposition.py