Generate a string of choices as key/value pairs
        :return: string

def _choices(self):
        """
        Generate a string of choices as key/value pairs
        :return: string
        """
        # Generate key/value strings
        pairs = []
        for key, value in self.choices.items():
            pairs.append(str(value) + "=" + str(key))

        # Assemble into overall string and escape
        return GPTaskSpec.manifest_escape(";".join(pairs))