Insert item into hash table with specified key and item.
If key is already present returns -1 and leaves existing item unchanged
Returns 0 on success.

def insert(self, key, item):
        """
        Insert item into hash table with specified key and item.
If key is already present returns -1 and leaves existing item unchanged
Returns 0 on success.
        """
        return lib.zhash_insert(self._as_parameter_, key, item)