<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def index_row(a:Union[Collection,pd.DataFrame,pd.Series], idxs:Collection[int])->Any:
    "Return the slice of `a` corresponding to `idxs`."
    if a is None: return a
    if isinstance(a,(pd.DataFrame,pd.Series)):
        res = a.iloc[idxs]
        if isinstance(res,(pd.DataFrame,pd.Series)): return res.copy()
        return res
    return a[idxs]