code: private Field getPartitionKeyField()
      {
          Field[] embeddedFields = entityMetadata.getIdAttribute().getBindableJavaType().getDeclaredFields();
  
          Field field = null;
          for (Field embeddedField : embeddedFields)
          {
              if (!ReflectUtils.isTransientOrStatic(embeddedField))
              {
                  field = embeddedField;
                  break;
              }
          }
          return field;
      }
docs: Will return partition key part of composite id.
  
  @return the partition key field