code: public <KEY> Where<KEY> where(KeySelector<T1, KEY> keySelector, TypeInformation<KEY> keyType)  {
  		requireNonNull(keySelector);
  		requireNonNull(keyType);
  		return new Where<>(input1.clean(keySelector), keyType);
  	}
docs: Specifies a {@link KeySelector} for elements from the first input with explicit type information for the key type.
  
  @param keySelector The KeySelector to be used for extracting the first input's key for partitioning.
  @param keyType The type information describing the key type.