I'm trying to write a C++ unit test that accesses a populated arrow::Table, where the table contains a column with a 2-D matrix, i.e. each row has a list(list(double)). I haven't been able to figure out how to access that data to finish this unit test. I am getting stuck here:

auto cmat = table->GetColumnByName("mat");
auto lmat = std::static_pointer_cast<arrow::ListArray>(cmat->chunk(0))
// How do I get from the parent ListArray to the child ListArrays?

I took a look at https://arrow.apache.org/docs/cpp/examples/row_columnar_conversion.html, but couldn't quite map it to my use case. Thanks,