'Retrieves the item inventory size
:return: Nothing.
:rtype: None'

def retrieve_inventories_size(self):

    if ((self.item_inventory_size is None) or (self.pokemon_inventory_size is None)):
        request = self.bot.api.create_request()
        request.get_player()
        player_data = request.call()['responses']['GET_PLAYER']['player_data']
        self.item_inventory_size = player_data['max_item_storage']
        self.pokemon_inventory_size = player_data['max_pokemon_storage']
