struct ConstValue
{
    static const char *name() { return "ConstValue"; }
    GRunArg arg;
};

auto p = cv::gapi::serialize(cv::GComputation(GIn(a), GOut(cv::gapi::addC(a,10))));
...
auto p = cv::gapi::serialize(cv::GComputation(GIn(a), GOut(a+10)))
...
auto p = cv::gapi::serialize(cv::GComputation(a, a+10));
...
// then
auto c = cv::gapi::deserialize<cv::GComputation>(p);
// and then
c.apply(cv::gin(in_mat /*, 10 */), cv::gout(out_mat));   // without `10` in runargs, `in_mat` only

force_builders=Custom,Custom Win,Custom Mac
build_gapi_standalone:Linux x64=ade-0.1.1f
build_gapi_standalone:Win64=ade-0.1.1f
build_gapi_standalone:Mac=ade-0.1.1f
build_gapi_standalone:Linux x64 Debug=ade-0.1.1f
build_image:Custom=centos:7
buildworker:Custom=linux-1
build_gapi_standalone:Custom=ade-0.1.1f
Xbuild_image:Custom=ubuntu-openvino-2021.3.0:20.04
build_image:Custom Win=openvino-2021.2.0
build_image:Custom Mac=openvino-2021.2.0
test_modules:Custom=gapi,python2,python3,java
test_modules:Custom Win=gapi,python2,python3,java
test_modules:Custom Mac=gapi,python2,python3,java
buildworker:Custom=linux-1
# disabled due high memory usage: test_opencl:Custom=ON
test_opencl:Custom=OFF
test_bigdata:Custom=1
test_filter:Custom=*