Refactor language update (#4316)

* refactor: separate formatting docs and golds in Language.update

* fix return typo

spacy/language.py

@@ -449,29 +449,9 @@ class Language(object):
     def make_doc(self, text):
         return self.tokenizer(text)
 
-    def update(self, docs, golds, drop=0.0, sgd=None, losses=None, component_cfg=None):
-        """Update the models in the pipeline.
-
-        docs (iterable): A batch of `Doc` objects.
-        golds (iterable): A batch of `GoldParse` objects.
-        drop (float): The droput rate.
-        sgd (callable): An optimizer.
-        losses (dict): Dictionary to update with the loss, keyed by component.
-        component_cfg (dict): Config parameters for specific pipeline
-            components, keyed by component name.
-
-        DOCS: https://spacy.io/api/language#update
-        """
+    def _format_docs_and_golds(self, docs, golds):
+        """Format golds and docs before update models."""
         expected_keys = ("words", "tags", "heads", "deps", "entities", "cats", "links")
-        if len(docs) != len(golds):
-            raise IndexError(Errors.E009.format(n_docs=len(docs), n_golds=len(golds)))
-        if len(docs) == 0:
-            return
-        if sgd is None:
-            if self._optimizer is None:
-                self._optimizer = create_default_optimizer(Model.ops)
-            sgd = self._optimizer
-        # Allow dict of args to GoldParse, instead of GoldParse objects.
         gold_objs = []
         doc_objs = []
         for doc, gold in zip(docs, golds):
@@ -485,8 +465,32 @@ class Language(object):
                 gold = GoldParse(doc, **gold)
             doc_objs.append(doc)
             gold_objs.append(gold)
-        golds = gold_objs
-        docs = doc_objs
+
+        return doc_objs, gold_objs
+
+    def update(self, docs, golds, drop=0.0, sgd=None, losses=None, component_cfg=None):
+        """Update the models in the pipeline.
+
+        docs (iterable): A batch of `Doc` objects.
+        golds (iterable): A batch of `GoldParse` objects.
+        drop (float): The droput rate.
+        sgd (callable): An optimizer.
+        losses (dict): Dictionary to update with the loss, keyed by component.
+        component_cfg (dict): Config parameters for specific pipeline
+            components, keyed by component name.
+
+        DOCS: https://spacy.io/api/language#update
+        """
+        if len(docs) != len(golds):
+            raise IndexError(Errors.E009.format(n_docs=len(docs), n_golds=len(golds)))
+        if len(docs) == 0:
+            return
+        if sgd is None:
+            if self._optimizer is None:
+                self._optimizer = create_default_optimizer(Model.ops)
+            sgd = self._optimizer
+        # Allow dict of args to GoldParse, instead of GoldParse objects.
+        docs, golds = self._format_docs_and_golds(docs, golds)
         grads = {}
 
         def get_grads(W, dW, key=None):