How to use the gillespy2.Reaction function in gillespy2

Build a GillesPy2 reaction.

        Attributes
        ----------
        args : dict
            A json representation of a reaction.
        parameters : list
            List of GillesPy2 parameters.
        '''
        if args['reactionType'] not in 'custom-propensity':
            rate = list(filter(lambda p: p.name == args['rate']['name'], parameters))[0]
            propensity = None
        else:
            rate = None
            propensity = args['propensity']
        R = Reaction(
            name=args['name'],
            reactants=self.build_stoich_species_dict(args['reactants']),
            products=self.build_stoich_species_dict(args['products']),
            rate=rate,
            propensity_function=propensity
        )
        return R