Fix Inheritance Issue

[PythonFZ]

• fix Can not inherit from Node #266

ToDo

• add tests to show the issue
• fix the issue
• fix issue with calling two Child Nodes after each other and loading the wrong results (see PassingClasses.ipynb) (This is partially fixed and mentioned in the documentation)
• update documentation

[codecov]

Codecov Report

Merging #267 (d0f83c3) into main (b955e06) will decrease coverage by 0.12%.
The diff coverage is 84.12%.

@@            Coverage Diff             @@
##             main     #267      +/-   ##
==========================================
- Coverage   72.36%   72.23%   -0.13%     
==========================================
  Files          26       26              
  Lines        1118     1149      +31     
  Branches      216      226      +10     
==========================================
+ Hits          809      830      +21     
- Misses        286      293       +7     
- Partials       23       26       +3     

Flag	Coverage Δ
unittests	72.23% <84.12%> (-0.13%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
zntrack/zn/__init__.py	77.77% <0.00%> (-4.58%)	⬇️
zntrack/utils/file_io.py	84.31% <71.42%> (-2.05%)	⬇️
zntrack/core/dvcgraph.py	68.91% <77.77%> (-1.75%)	⬇️
zntrack/descriptor/__init__.py	95.55% <85.71%> (-4.45%)	⬇️
zntrack/core/base.py	90.00% <91.66%> (-0.91%)	⬇️
zntrack/core/zntrackoption.py	86.36% <100.00%> (ø)
zntrack/dvc/__init__.py	97.72% <100.00%> (+0.10%)	⬆️
zntrack/utils/utils.py	72.81% <100.00%> (+0.26%)	⬆️

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