Allows serialize / deserialize fields like objects.

Object should have opApply method to allow serialization. Following code should compile:

foreach(key, value; yourObject)
{
    ...
}

Object should have only one opApply method with 2 argument to allow automatic value type deduction.

opIndexAssign or opIndex is used for deserialization to support required syntax:

yourObject["key"] = value;

Multiple value types is supported for deserialization.