bring back dropped columns in pandas code example

Example 1: how to drop a column by name in pandas

>>> df.drop(columns=['B', 'C'])
   A   D
0  0   3
1  4   7
2  8  11

Example 2: how to drop a column by name in pandas

>>> df.drop(['B', 'C'], axis=1)
   A   D
0  0   3
1  4   7
2  8  11