@Override
        public String toString() {
          return "(<=> " + inType + ", " + rank + ", " + ordering + ")";
        }
While we have {@link SourceOrdering}, there's still a problem: We have inheritance hierarchy,
and we want to have all defined or inherited accessors returned as members of target type,
like {@link Elements#getAllMembers(TypeElement)},
but we need to have them properly and stably sorted.
This implementation doesn't try to correctly resolve order for accessors inherited from
different supertypes(interfaces), just something that stable and reasonable wrt source ordering
without handling complex cases.
@param elements the elements utility
@param types the types utility
@param originatingType the type to traverse
@param useLegacyAccessorOrdering switch to legacy, pre 2.7.5 accessor ordering
@return provider of all accessors in source order and mapping
generator/src/org/immutables/generator/SourceOrdering.java