Method __len__

crates/vm/src/builtins/mappingproxy.rs:180–183

(&self, vm: &VirtualMachine)

    }

    fn __len__(&self, vm: &VirtualMachine) -> PyResult<usize> {
        let obj = self.to_object(vm)?;
        obj.length(vm)
    }

    #[pymethod]
    fn __reversed__(&self, vm: &VirtualMachine) -> PyResult {