Fix too many values to unpack error (#13511)

* fix too many values to unpack error

In the example script lstm_seq2seq_restore.py and lstm_seq2seq.py, when
parse the data using line.split("\t"), it will return 3 values rather than
2, a simple modification can fix it.

* add blankspace around operator

examples/lstm_seq2seq.py

@@ -70,7 +70,7 @@ target_characters = set()
 with open(data_path, 'r', encoding='utf-8') as f:
     lines = f.read().split('\n')
 for line in lines[: min(num_samples, len(lines) - 1)]:
-    input_text, target_text = line.split('\t')
+    input_text, target_text, _ = line.split('\t')
     # We use "tab" as the "start sequence" character
     # for the targets, and "\n" as "end sequence" character.
     target_text = '\t' + target_text + '\n'

examples/lstm_seq2seq_restore.py

@@ -33,7 +33,7 @@ target_characters = set()
 with open(data_path, 'r', encoding='utf-8') as f:
     lines = f.read().split('\n')
 for line in lines[: min(num_samples, len(lines) - 1)]:
-    input_text, target_text = line.split('\t')
+    input_text, target_text, _ = line.split('\t')
     # We use "tab" as the "start sequence" character
     # for the targets, and "\n" as "end sequence" character.
     target_text = '\t' + target_text + '\n'