Make sure our coal, if we have any, is in slot 0.

def checkFuelPosition(obs, agent_host):
    '''Make sure our coal, if we have any, is in slot 0.'''
    # (We need to do this because the furnace crafting commands - cooking the potato and the rabbit -
    # take the first available item of fuel in the inventory. If this isn't the coal, it could end up burning the wood
    # that we need for making the bowl.)
    for i in range(1,39):
        key = 'InventorySlot_'+str(i)+'_item'
        if key in obs:
            item = obs[key]
            if item == 'coal':
                agent_host.sendCommand("swapInventoryItems 0 " + str(i))
                return