Set wrapper for the entrySet method. Entry objects are wrapped further in JavaToPyMapEntry and PyToJavaMapEntry. Note - The set interface is reliable for standard objects like strings and integers, but may be inconsistent for other types of objects since the equals method may return false for Entry object that hold more elaborate PyObject types. However, we insure that this interface works when the Entry object originates from a Set object retrieved from a PyDictionary.