id1       date_time               adress       a_size
 reom      2005-8-20 22:51:10      75157.5413   ceifwekd
 reom      2005-8-20 22:55:25      3571.37946   ceifwekd
 reom      2005-8-20 11:21:01      3571.37946   tnohcve
 reom      2005-8-20 11:22:09      97439.219    tnohcve
 reom      2005-8-20 11:25:09      97439.219    efgrcaw
 penr      2005-8-20 17:07:16     97439.219    ceifwekd
 penr      2005-8-20 19:10:37      7391.6258    ceifwekd
 ....

id1       date_time               adress       a_size         max_transaction
 reom      2005-8-20 22:51:10      75157.5413   ceifwekd         2
 reom      2005-8-20 22:55:25      3571.37946   ceifwekd         2
 reom      2005-8-20 11:21:01      3571.37946   tnohcve          3
 reom      2005-8-20 11:22:09      97439.219    tnohcve          3
 reom      2005-8-20 11:25:09      97439.219    efgrcaw          3
 penr      2005-8-20 17:07:16     97439.219    ceifwekd          1
 penr      2005-8-20 19:10:37      7391.6258    ceifwekd         1

reom      2005-8-20 11:21:01      3571.37946   tnohcve          3
reom      2005-8-20 11:22:09      97439.219    tnohcve          3
reom      2005-8-20 11:25:09      97439.219    efgrcaw          3

df['num_per_10_min'] = df.groupby(['id1',df['date_time'].dt.floor('10Min')])['date_time'].agg('count')

TypeError: incompatible index of inserted column with frame index