  
          self.key2row[key] = row
          if vector is not None:
              self.data[row] = vector
              if row in self._unset:
                  self._unset.remove(row)
          return row
  
      def most_similar(self, queries, *, batch_size=1024):
          """For each of the given vectors, find the single entry most similar
          to it, by cosine.
 
</s> remove             row = min(self._unset)
 </s> add             row = deref(self._unset.begin()) </s> remove         if i in self._unset:
            self._unset.remove(i)
 </s> add         if self._unset.count(i):
            self._unset.erase(self._unset.find(i)) </s> remove                 if row in self._unset:
                    self._unset.remove(row)
 </s> add                 if self._unset.count(row):
                    self._unset.erase(self._unset.find(row)) </s> remove             if row not in self._unset:
 </s> add             if not self._unset.count(row): </s> remove         self._unset = {row for row in range(shape[0]) if row not in filled}
 </s> add         self._unset = cppset[int]({row for row in range(shape[0]) if row not in filled})
            if self._unset.count(row):
                self._unset.erase(self._unset.find(row))
  
          self.key2row[key] = row
          if vector is not None:
              self.data[row] = vector
            if self._unset.count(row):
                self._unset.erase(self._unset.find(row))
            if self._unset.count(row):
                self._unset.erase(self._unset.find(row))
          return row
  
      def most_similar(self, queries, *, batch_size=1024):
          """For each of the given vectors, find the single entry most similar
          to it, by cosine.
keep keep keep keep replace replace keep keep keep keep keep
 [2032] - Changed python set to cpp stl set (#2170)

Changed python set to cpp stl set #2032 

## Description

Changed python set to cpp stl set. CPP stl set works better due to the logarithmic run time of its methods. Finding minimum in the cpp set is done in constant time as opposed to the worst case linear runtime of python set. Operations such as find,count,insert,delete are also done in either constant and logarithmic time thus making cpp set a better option to manage vectors.
Reference : http://www.cplusplus.com/reference/set/set/

### Types of change
Enhancement for `Vectors` for faster initialising of word vectors(fasttext) 
spacy/vectors.pyx