パンダで GroupBy を使用するときに他の列を保持する方法は?

<code class="python">df_filtered = df.loc[df.groupby("item")["diff"].idxmin()]</code>

<code class="python">df_filtered = df.sort_values("diff").groupby("item", as_index=False).first()</code>

<code class="python">df = pd.DataFrame({"item": [1, 1, 1, 2, 2, 2, 2, 3, 3],
                   "diff": [2, 1, 3, -1, 1, 4, -6, 0, 2],
                   "otherstuff": [1, 2, 7, 0, 3, 9, 2, 0, 9]})

# Method 1
df_filtered1 = df.loc[df.groupby("item")["diff"].idxmin()]

# Method 2
df_filtered2 = df.sort_values("diff").groupby("item", as_index=False).first()

print(df_filtered1)
print(df_filtered2)</code>

   item  diff  otherstuff
1     1     1           2
6     2    -6           2
7     3     0           0

   item  diff  otherstuff
0     1     1           2
1     2    -6           2
2     3     0           0