<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def remove(self, item):
 """Remove an item from the set. Inverts the add operation. ['eggs'] """

        if item in self:
            super(NGram, self).remove(item)
            del self.length[item]
            for ngram in self.splititem(item):
                del self._grams[ngram][item]