Pad and mask the sequences in each batch

src/hyperparameters.py

@@ -11,6 +11,7 @@ class Hyperparameters:
         learning_rate=0.004,
         l2_rate=0.001,
         log_directory="logs",
+        max_length=80,
     ):
         self.data_file = data_file
         self.label_file = label_file
@@ -22,3 +23,4 @@ class Hyperparameters:
         self.learning_rate = learning_rate
         self.l2_rate = l2_rate
         self.log_directory = log_directory
+        self.max_length = max_length