count number rows with groupby pandas

I had the following function in pandas 0.17:

df['numberrows'] = df.groupby(['column1','column2','column3'], as_index=False)[['column1']].transform('count').astype('int')

But I upgraded pandas today and now I get the error:

  File "/usr/local/lib/python3.4/dist-packages/pandas/core/internals.py",

line 3810, in insert raise ValueError('cannot insert {}, already exists'.format(item))

ValueError: cannot insert column1, already exists

What has changed in the update which causes this function to not work anymore?

I want to groupby the columns and add a column which has the amount or rows of the groupby.

If what I did before was not a good function, another way of grouping while getting the amount of rows that were grouped is also welcome.

EDIT:

small dataset:

    column1  column2    column3   
 0  test     car1       1           
 1  test2    car5       2         
 2  test     car1       1         
 3  test4    car2       1      
 4  test2    car1       1         

outcome would be:

    column1  column2    column3   numberrows
 0  test     car1       1           2
 1  test2    car5       2           1     
 3  test4    car2       1           1
 4  test2    car1       1           1