isEqual method
Compares this object with the given object for equality.
This object is considered "equal" to the other object if and only if
other
performs the same kind of aggregation on the same field (if any).
@param other The object to compare to this object for equality.
@return true
if this object is "equal" to the given object, as
defined above, or false
otherwise.
Implementation
external bool isEqual(AggregateField other);