get_nivel_region() function not defined

[ASG09]

Describe the bug
When using the timeseries.py function, the functionality supposed to group the returned values from the request (arg named "groupby") is not working properly, as the function named get_nivel_region() used within is not defined.

To Reproduce

1. Example to get the error:
   '''
   import json
   import requests
   import ipeadatapy as ipea

big_theme = 'Regional'
theme_id = 6
keyword = 'Receita tributária - municipal'
name = ipea.list_series(keyword=keyword)['NAME'][0]
seriesCode = ipea.list_series(keyword=keyword)['CODE'][0]

myData = ipea.metadata(series=seriesCode, big_theme=big_theme, source=None, country=None, frequency=None, unit=None, measure=None, status=None, source_ext=None, source_url=None, last_update=None, code=None, comment=None, name=None, numerica=None, theme_id=theme_id)

if len(myData)==1:
myValues=ipea.timeseries(series=seriesCode, year=2017, grouby='TERNOME')
'''

Expected behaviour
I'm not sure how the groupby argument can group the results, perhaps it would create instances of the data frame, grouped by the grouping criteria ('TERNOME', territory name in this case).

Desktop (please complete the following information):

• OS: Windows10
• Browser Microsoft Edge
• Version 85.0.564.63