Intercept call of joinpoint callee in doing pre/post conditions.

def _interception(self, joinpoint):
        """Intercept call of joinpoint callee in doing pre/post conditions.
        """

        if self.pre_cond is not None:
            self.pre_cond(joinpoint)

        result = joinpoint.proceed()

        if self.post_cond is not None:
            joinpoint.exec_ctx[Condition.RESULT] = result
            self.post_cond(joinpoint)

        return result