Variant().Build()

[asmyasnikov]

This is root Variant type builder which will have methods

1. construct intermedite object for tuple:

   ydb.ParamsBuilder().Param("$p1").Variant().Tuple().
       /*sub calls of tuple builder*/
       Build()

2. construct intermedite object for struct:

   ydb.ParamsBuilder().Param("$p1").Variant().Struct().
       /*sub calls of struct builder*/
       Build()