'evaluates expression in current context and returns its value
as opposed to the (faster) self.execute method, you can use your regular debugger
to set breakpoints and inspect the generated python code'

def eval_debug(self, expression):

    code = ('PyJsEvalResult    =    eval(%s)' % json.dumps(expression))
    self.execute_debug(code)
    return self['PyJsEvalResult']
