code: def finditem(self, item, threshold=None):
          
          results = self.searchitem(item, threshold)
          if results:
              return results[0][0]
          else:
              return None
docs: Return most similar item to the provided one, or None if
          nothing exceeds the threshold.
  
          >>> from ngram import NGram
          >>> n = NGram([(0, "Spam"), (1, "Ham"), (2, "Eggsy"), (3, "Egggsy")],
          ...     key=lambda x:x[1].lower())
          >>> n.finditem((3, 'Hom'))
          (1, 'Ham')
          >>> n.finditem((4, "Oggsy"))
          (2, 'Eggsy')
          >>> n.finditem((4, "Oggsy"), 0.8)