CustomBusinessMonthBegin offset parameter

[LingnanLemon]

Code Sample, a copy-pastable example if possible

from pandas.tseries.offsets import CustomBusinessMonthBegin
 
my_offset= CustomBusinessMonthBegin(offset=timedelta(days=5))

Problem description

when creating the offset instance with specific day offset, shows 'offset' is an invalid keyword.

Expected Output

Trying to use the CustomBusinessMonthBegin together with my customized calender and a day offset to get the N_th business day of a certain calender.
Return value should be a caloffset instance.
MonthBegin to get the first business day works well. What if I want to get the second/third/...n_th business day?

Output of pd.show_versions()

0.18.0

# Paste the output here pd.show_versions() here

[UltaLior]

Isnt this a bug?

[mroeschke]

This looks fixed on master. I guess it could use a test

In [19]: from datetime import timedelta

In [20]: from pandas.tseries.offsets import CustomBusinessMonthBegin
    ...:
    ...: my_offset= CustomBusinessMonthBegin(offset=timedelta(days=5))

In [21]: my_offset
Out[21]: <CustomBusinessMonthBegin: offset=datetime.timedelta(days=5)>

[jackzyliu]

First time contributing here. Mind if I take this one?

[mroeschke]

Closed by #41488