Using python class instances in python from c++ (boost)

Question

I'm looking for a way how to create an instance of a class written in python and call it's methods from c++. If available, I'd prefer to incldue the boost python libraries. I imagine to have a class in python like

class MyPythonClass(object):
    def __init__(self, first_var):
        self.__varToStore = first_var
    def method_to_call(self, list_of_input = []):
        ### some manipulation
        return 42

I've already found lot's of threads, how to import the python module in c++ using the python libraries and may-be I've found a way how to create an instance of the class.

boost::python::object mylib = boost::python::import("MyModule");
boost::python::object my_class = mylib.attr("MyPythonClass");

But from that point, I'm just stuck. How can I create an instance of the class and call its method?

Thanks