* Add missing __contains__ method to vocab

spacy/strings.pyx

@@ -118,6 +118,11 @@ cdef class StringStore:
         else:
             raise TypeError(type(string_or_id))
 
+    def __contains__(self, unicode string):
+        cdef hash_t key = hash_string(string)
+        value = <Utf8Str*>self._map.get(key)
+        return True if value is not NULL else False
+
     def __iter__(self):
         cdef int i
         for i in range(self.size):

spacy/tests/vocab/test_vocab.py

@@ -45,6 +45,11 @@ def test_symbols(en_vocab):
     assert en_vocab.strings['PROB'] == PROB
 
 
+def test_contains(en_vocab):
+    assert 'Hello' in en_vocab
+    assert 'LKsdjvlsakdvlaksdvlkasjdvljasdlkfvm' not in en_vocab
+    
+
 @pytest.mark.xfail
 def test_pickle_vocab(en_vocab):
     file_ = io.BytesIO()

spacy/vocab.pyx

@@ -172,6 +172,11 @@ cdef class Vocab:
         self._by_orth.set(lex.orth, <void*>lex)
         self.length += 1
 
+    def __contains__(self, unicode string):
+        key = hash_string(string)
+        lex = self._by_hash.get(key)
+        return True if lex is not NULL else False
+
     def __iter__(self):
         cdef attr_t orth
         cdef size_t addr