Models of the ObjectWrapper concept have object as a publicly-accessible base class, and are used to supply special construction behavior and/or additional convenient functionality through (often templated) member functions. Except when the return type R is itself an TypeWrapper, a member function invocation of the form

x.some_function(a1, a2,...an)

always has semantics equivalent to:

extract<R>(x.attr("some_function")(object(a1), object(a2),...object(an)))()

(see caveat below).