Validates that the indices have values within range of num_qubits.

def _validate_indices(num_qubits: int, indices: List[int]) -> None:
    """Validates that the indices have values within range of num_qubits."""
    if any(index < 0 for index in indices):
        raise IndexError('Negative index in indices: {}'.format(indices))
    if any(index >= num_qubits for index in indices):
        raise IndexError('Out of range indices, must be less than number of '
                         'qubits but was {}'.format(indices))