code: private void addToOverrideMap(ExecutableElement methodElement) {
      String overrideID = stitchOverrideMethodIdentifier(methodElement);
      if (overrideMap.containsKey(overrideID)) {
        overrideMap.get(overrideID).add(stitchMethodIdentifier(methodElement));
      } else {
        HashSet<String> overrideSet = new HashSet<String>();
        overrideSet.add(stitchMethodIdentifier(methodElement));
        overrideMap.put(overrideID, overrideSet);
      }
    }
docs: Adds the common IDs of overriding methods (methodName and signature) to the override map.
  @param methodElement