convert list of list to np.array

peak_signal_to_noise_ratio.py

@@ -90,7 +90,7 @@ class PeakSignaltoNoiseRatio(evaluate.Metric):
         data_range: Optional[float] = None, 
         sample_weight=None,
     ) -> Dict[str, float]:
-        samples = zip(predictions, references)
+        samples = zip(np.ndarray(predictions), np.ndarray(references))
         psnrs = list(map(
             lambda args: peak_signal_noise_ratio(*args, data_range=data_range), samples
         ))