public PdxType getPdxTypeForField(String fieldName, String className) {
    return distributedTypeRegistry.getPdxTypeForField(fieldName, className);
  }
searches a field in different versions (PdxTypes) of a class in the distributed type registry

@param fieldName the field to look for in the PdxTypes
@param className the PdxTypes for this class would be searched
@return PdxType having the field or null if not found
geode-core/src/main/java/org/apache/geode/pdx/internal/TypeRegistry.java