Add minibatch function in spacy.gold

spacy/gold.pyx

@@ -6,6 +6,7 @@ import io
 import re
 import ujson
 import random
+import cytoolz
 
 from .syntax import nonproj
 from .util import ensure_path
@@ -141,6 +142,19 @@ def _min_edit_path(cand_words, gold_words):
     return prev_costs[n_gold], previous_row[-1]
 
 
+def minibatch(items, size=8):
+    '''Iterate over batches of items. `size` may be an iterator,
+    so that batch-size can vary on each step.
+    '''
+    items = iter(items)
+    while True:
+        batch_size = next(size) #if hasattr(size, '__next__') else size
+        batch = list(cytoolz.take(int(batch_size), items))
+        if len(batch) == 0:
+            break
+        yield list(batch)
+
+
 class GoldCorpus(object):
     """An annotated corpus, using the JSON file format. Manages
     annotations for tagging, dependency parsing and NER."""
@@ -396,7 +410,10 @@ cdef class GoldParse:
             else:
                 self.words[i] = words[gold_i]
                 self.tags[i] = tags[gold_i]
-                self.heads[i] = self.gold_to_cand[heads[gold_i]]
+                if heads[gold_i] is None:
+                    self.heads[i] = None
+                else:
+                    self.heads[i] = self.gold_to_cand[heads[gold_i]]
                 self.labels[i] = deps[gold_i]
                 self.ner[i] = entities[gold_i]