Fails the transaction if Key does not have a modify index equal to
        Index

        Parameters:
            key (str): Key to check
            index (ObjectIndex): Index ID

def check_index(self, key, *, index):
        """Fails the transaction if Key does not have a modify index equal to
        Index

        Parameters:
            key (str): Key to check
            index (ObjectIndex): Index ID
        """
        self.append({
            "Verb": "check-index",
            "Key": key,
            "Index": extract_attr(index, keys=["ModifyIndex", "Index"])
        })
        return self