private Object readResolve() throws ObjectStreamException {
    return INSTANCE;
  }
An implementation of {@link ObjectSizer} that calculates an accurate, in memory size of for the
first instance of each class that it sees. After the first size calculation, it will return the
same size for every instance of that class.

This sizer is a compromise between generating accurate sizes for every object and performance. It
should work well for objects that are fairly constant in size. For completely accurate sizing,
use {@link ReflectionObjectSizer}
geode-core/src/main/java/org/apache/geode/internal/size/SizeClassOnceObjectSizer.java