code: public LegacyObjectMapType getOrCreateLegacyObjectMapType(SoyType keyType, SoyType valueType) {
      return legacyObjectMapTypes.intern(LegacyObjectMapType.of(keyType, valueType));
    }
docs: Factory function which creates a legacy object map type, given a key and value type. This folds
  map types with identical key/value types together, so asking for the same key/value type twice
  will return a pointer to the same type object.
  
  @param keyType The key type of the map.
  @param valueType The value type of the map.
  @return The map type.