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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def grab_idx(x,i,batch_first:bool=True):
    "Grab the `i`-th batch in `x`, `batch_first` stating the batch dimension."
    if batch_first: return ([o[i].cpu() for o in x]   if is_listy(x) else x[i].cpu())
    else:           return ([o[:,i].cpu() for o in x] if is_listy(x) else x[:,i].cpu())