code: public SingleOutputStreamOperator<T> maxBy(String field, boolean first) {
  		return aggregate(new ComparableAggregator<>(field, getType(), AggregationFunction.AggregationType.MAXBY,
  				first, getExecutionConfig()));
  	}
docs: Applies an aggregation that gives the current maximum element of the
  data stream by the given field expression by the given key. An
  independent aggregate is kept per key. A field expression is either the
  name of a public field or a getter method with parentheses of the
  {@link DataStream}'s underlying type. A dot can be used to drill down into
  objects, as in {@code "field1.fieldxy" }.
  
  @param field
  In case of a POJO, Scala case class, or Tuple type, the
  name of the (public) field on which to perform the aggregation.
  Additionally, a dot can be used to drill down into nested
  objects, as in {@code "field1.fieldxy" }.
  Furthermore "*" can be specified in case of a basic type
  (which is considered as having only one field).
  @param first
  If True then in case of field equality the first object will
  be returned
  @return The transformed DataStream.