Hidden property doesn't work as expected.

[dev-mkc19]

Hi. Release 0.10 brought ability to get status of field, either it hidden or not. But in fact Tableau workbook doesn't contain xml attribute for every field, only for hidden. So after initialisation Workbook object if you check fields you will see two values False or None.

But code and docstring inside hidden method tells that as a user I should expect only True False values. Am I right that it's a bug and None values have to be handled?

Code to reproduce:

import tableaudocumentapi
wb = tableaudocumentapi.Workbook('CheckBook_2021.2_sql.twb')
import pandas as pd

fs = []
for s in wb.datasources:
 for k in s.fields:
 try:
 id = s.fields[k].id
 except:
 pass
 try:
 name = s.fields[k].name
 except:
 pass
 try:
 caption = s.fields[k].caption
 except:
 pass
 try:
 calculation = s.fields[k].calculation
 except:
 pass
 try:
 hidden = s.fields[k].hidden
 except:
 pass


 fs.append({'ds': s.caption,
 'id': id,
 'name': name,
 'caption': caption,
 'calculation': calculation,
 'hidden': hidden
 })
df = pd.DataFrame.from_records(fs)
df

Result:

CheckBook_2021.2_sql.twb.zip