Returns the number of keys in object o on success, and -1 on failure. For objects that do not provide mapping protocol, this is equivalent to the Python expression len(o).
On success, return a list of the keys in object o. On failure, return NULL. This is equivalent to the Python expression list(o.keys()).
On success, return a list of the values in object o. On failure, return NULL. This is equivalent to the Python expression list(o.values()).
On success, return a list of the items in object o, where each item is a tuple containing a key-value pair. On failure, return NULL. This is equivalent to the Python expression list(o.items()).