Fetch an output from the designated stack.

        Args:
            value (str): string with the following format:
                <stack_name>::<output_name>, ie. some-stack::SomeOutput
            provider (:class:`stacker.provider.base.BaseProvider`): subclass of
                the base provider

        Returns:
            str: output from the specified stack

def handle(cls, value, provider=None, **kwargs):
        """Fetch an output from the designated stack.

        Args:
            value (str): string with the following format:
                <stack_name>::<output_name>, ie. some-stack::SomeOutput
            provider (:class:`stacker.provider.base.BaseProvider`): subclass of
                the base provider

        Returns:
            str: output from the specified stack
        """

        if provider is None:
            raise ValueError('Provider is required')

        d = deconstruct(value)
        stack_fqn = d.stack_name
        output = provider.get_output(stack_fqn, d.output_name)
        return output