Add dummy serialization methods for Japanese and missing lang getter (resolves #1557)

spacy/lang/ja/__init__.py

@@ -21,8 +21,25 @@ class JapaneseTokenizer(object):
         words = [x.surface for x in self.tokenizer.tokenize(text)]
         return Doc(self.vocab, words=words, spaces=[False]*len(words))
 
+    # add dummy methods for to_bytes, from_bytes, to_disk and from_disk to
+    # allow serialization (see #1557)
+    def to_bytes(self, **exclude):
+        return b''
+
+    def from_bytes(self, bytes_data, **exclude):
+        return self
+
+    def to_disk(self, path, **exclude):
+        return None
+
+    def from_disk(self, path, **exclude):
+        return self
+
 
 class JapaneseDefaults(Language.Defaults):
+    lex_attr_getters = dict(Language.Defaults.lex_attr_getters)
+    lex_attr_getters[LANG] = lambda text: 'ja'
+
     @classmethod
     def create_tokenizer(cls, nlp=None):
         return JapaneseTokenizer(cls, nlp)