code: public static void serializeUserProperties( BackendlessUser user )
    {
      Map<String, Object> serializedProperties = user.getProperties();
  
      Set<Map.Entry<String, Object>> properties = serializedProperties.entrySet();
      for( Map.Entry<String, Object> property : properties )
      {
        Object propertyValue = property.getValue();
        if( propertyValue != null && !propertyValue.getClass().isArray() && !propertyValue.getClass().isEnum() && !isBelongsJdk( propertyValue.getClass() ) )
        {
          property.setValue( serializeToMap( propertyValue ) );
        }
      }
  
      user.setProperties( serializedProperties );
    }
docs: Serializes entities inside BackendlessUser properties.
  
  @param user BackendlessUser whose properties need to be serialized