Add example showing a fix-up rule for space entities

examples/pipeline/fix_space_entities.py

@@ -0,0 +1,27 @@
+'''Demonstrate adding a rule-based component that forces some tokens to not
+be entities, before the NER tagger is applied. This is used to hotfix the issue
+in https://github.com/explosion/spaCy/issues/2870 , present as of spaCy v2.0.16.
+'''
+import spacy
+from spacy.attrs import ENT_IOB
+
+def fix_space_tags(doc):
+    ent_iobs = doc.to_array([ENT_IOB])
+    for i, token in enumerate(doc):
+        if token.is_space:
+            # Sets 'O' tag (0 is None, so I is 1, O is 2)
+            ent_iobs[i] = 2
+    doc.from_array([ENT_IOB], ent_iobs.reshape((len(doc), 1)))
+    return doc
+
+def main():
+    nlp = spacy.load('en_core_web_sm')
+    text = u'''This is some crazy test where I dont need an Apple                Watch to make things bug'''
+    doc = nlp(text)
+    print('Before', doc.ents)
+    nlp.add_pipe(fix_space_tags, name='fix-ner', before='ner')
+    doc = nlp(text)
+    print('After', doc.ents)
+
+if __name__ == '__main__':
+    main()