def METHOD_NAME(self, labels, predictions):
    """
    Args:
        labels: list or numpy.array with the qubit labels of the quantum states to be classified
        predictions: list or numpy.array with the qubit predictions for the quantum states to be classified
    Returns:
        numpy.float32 with the value of the square-loss function
    """
    loss = 0
    for l, p in zip(labels, predictions):
        for qubit in range(self.measured_qubits):
            loss += (l[qubit] - p[qubit]) ** 2
    return loss / len(labels)