I have a dataframe which consists of a couple of columns with same name i.e.

items_group quanity items_group quanity 
KIT1259 0       
KIT1260 0       
KIT1261 0       
                       KIT1151  1
                       KIT1198A 4
                       KIT1198D 5
                       KIT1243  29
                       KIT1249  8

How do I merge them and have only one column of each?
I tried

    df_expanded2 = df_expanded2.stack().dropna().unstack()

But this gives the following error sometimes:

Error:

Traceback (most recent call last):
  File "/Users/rahulsharma/PycharmProjects/Trakkia-Backend/venv/lib/python3.8/site-packages/django/core/handlers/exception.py", line 34, in inner
    response = get_response(request)
  File "/Users/rahulsharma/PycharmProjects/Trakkia-Backend/venv/lib/python3.8/site-packages/django/core/handlers/base.py", line 115, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "/Users/rahulsharma/PycharmProjects/Trakkia-Backend/venv/lib/python3.8/site-packages/django/core/handlers/base.py", line 113, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/Users/rahulsharma/PycharmProjects/Trakkia-Backend/venv/lib/python3.8/site-packages/django/views/decorators/csrf.py", line 54, in wrapped_view
    return view_func(*args, **kwargs)
  File "/Users/rahulsharma/PycharmProjects/Trakkia-Backend/venv/lib/python3.8/site-packages/django/views/generic/base.py", line 71, in view
    return self.dispatch(request, *args, **kwargs)
  File "/Users/rahulsharma/PycharmProjects/Trakkia-Backend/venv/lib/python3.8/site-packages/rest_framework/views.py", line 505, in dispatch
    response = self.handle_exception(exc)
  File "/Users/rahulsharma/PycharmProjects/Trakkia-Backend/venv/lib/python3.8/site-packages/rest_framework/views.py", line 465, in handle_exception
    self.raise_uncaught_exception(exc)
  File "/Users/rahulsharma/PycharmProjects/Trakkia-Backend/venv/lib/python3.8/site-packages/rest_framework/views.py", line 476, in raise_uncaught_exception
    raise exc
  File "/Users/rahulsharma/PycharmProjects/Trakkia-Backend/venv/lib/python3.8/site-packages/rest_framework/views.py", line 502, in dispatch
    response = handler(request, *args, **kwargs)
  File "/Users/rahulsharma/PycharmProjects/Trakkia-Backend copy/reports/views.py", line 1890, in get
    df_expanded2 = df_expanded2.stack().dropna().unstack()
  File "/Users/rahulsharma/PycharmProjects/Trakkia-Backend/venv/lib/python3.8/site-packages/pandas/core/series.py", line 4157, in unstack
    return unstack(self, level, fill_value)
  File "/Users/rahulsharma/PycharmProjects/Trakkia-Backend/venv/lib/python3.8/site-packages/pandas/core/reshape/reshape.py", line 491, in unstack
    unstacker = _Unstacker(
  File "/Users/rahulsharma/PycharmProjects/Trakkia-Backend/venv/lib/python3.8/site-packages/pandas/core/reshape/reshape.py", line 140, in __init__
    self._make_selectors()
  File "/Users/rahulsharma/PycharmProjects/Trakkia-Backend/venv/lib/python3.8/site-packages/pandas/core/reshape/reshape.py", line 192, in _make_selectors
    raise ValueError("Index contains duplicate entries, cannot reshape")
ValueError: Index contains duplicate entries, cannot reshape