original_string: public function distinctUntilChanged(callable $keySelector = null, callable $comparer = null)
      {
          return $this->lift(function () use ($keySelector, $comparer) {
              return new DistinctUntilChangedOperator($keySelector, $comparer);
          });
      }
code: public function distinctUntilChanged(callable $keySelector = null, callable $comparer = null)
      {
          return $this->lift(function () use ($keySelector, $comparer) {
              return new DistinctUntilChangedOperator($keySelector, $comparer);
          });
      }
code_tokens: public function distinctUntilChanged ( callable $ keySelector = null , callable $ comparer = null ) { return $ this -> lift ( function ( ) use ( $ keySelector , $ comparer ) { return new DistinctUntilChangedOperator ( $ keySelector , $ comparer ) ; } ) ; }
docstring: Returns an observable sequence that contains only distinct contiguous elements according to the keySelector
  and the comparer.
  
  @param callable $keySelector
  @param callable $comparer
  @return \Rx\Observable\AnonymousObservable
docstring_tokens: Returns an observable sequence that contains only distinct contiguous elements according to the keySelector and the comparer .