Fix concatenation in iob2json converter

spacy/cli/converters/iob2json.py

@@ -1,5 +1,6 @@
 # coding: utf8
 from __future__ import unicode_literals
+from cytoolz import partition_all, concat
 
 from ...compat import json_dumps, path2str
 from ...util import prints
@@ -10,22 +11,24 @@ def iob2json(input_path, output_path, n_sents=10, *a, **k):
     """
     Convert IOB files into JSON format for use with train cli.
     """
-    # TODO: This isn't complete yet -- need to map from IOB to
-    # BILUO
     with input_path.open('r', encoding='utf8') as file_:
-        docs = read_iob(file_)
+        if n_sents:
+            lines = [' '.join(para) for para in partition_all(n_sents, file_)]
+        else:
+            lines = file_
+    sentences = read_iob(lines)
 
     output_filename = input_path.parts[-1].replace(".iob", ".json")
     output_file = output_path / output_filename
     with output_file.open('w', encoding='utf-8') as f:
-        f.write(json_dumps(docs))
-    prints("Created %d documents" % len(docs),
+        f.write(json_dumps(sentences))
+    prints("Created %d documents" % len(sentences),
            title="Generated output file %s" % path2str(output_file))
 
 
-def read_iob(file_):
+def read_iob(raw_sents):
     sentences = []
-    for line in file_:
+    for line in raw_sents:
         if not line.strip():
             continue
         tokens = [t.split('|') for t in line.split()]