Fix custom_transform_and_model notebook

[Mr-Geekman]

IMPORTANT: Please do not create a Pull Request without creating an issue first.

Before submitting (must do checklist)

• Did you read the contribution guide?
• Did you update the docs? We use Numpy format for all the methods and classes.
• Did you write any new necessary tests?
• Did you update the CHANGELOG?

Type of Change

• Examples / docs / tutorials / contributors update
• Bug fix (non-breaking change which fixes an issue)
• Improvement (non-breaking change which improves an existing feature)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Proposed Changes

Look #627.

Related Issue

#627.

Closing issues

Closes #627.

[github-actions]

🚀 Deployed on https://deploy-preview-651--etna-docs.netlify.app

[codecov-commenter]

Codecov Report

Merging #651 (28c3b51) into master (8ade7d3) will decrease coverage by 31.78%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           master     #651       +/-   ##
===========================================
- Coverage   84.44%   52.65%   -31.79%     
===========================================
  Files         119      119               
  Lines        6320     6320               
===========================================
- Hits         5337     3328     -2009     
- Misses        983     2992     +2009     

Impacted Files	Coverage Δ
etna/commands/__init__.py	0.00% <0.00%> (-100.00%)	⬇️
etna/commands/backtest_command.py	0.00% <0.00%> (-96.43%)	⬇️
etna/commands/forecast_command.py	0.00% <0.00%> (-92.00%)	⬇️
etna/commands/__main__.py	0.00% <0.00%> (-87.50%)	⬇️
etna/commands/resolvers.py	0.00% <0.00%> (-80.00%)	⬇️
etna/analysis/outliers/density_outliers.py	22.44% <0.00%> (-75.52%)	⬇️
etna/datasets/datasets_generation.py	27.02% <0.00%> (-72.98%)	⬇️
etna/transforms/timestamp/time_flags.py	27.02% <0.00%> (-72.98%)	⬇️
etna/transforms/timestamp/fourier.py	28.57% <0.00%> (-71.43%)	⬇️
etna/transforms/missing_values/resample.py	25.00% <0.00%> (-71.43%)	⬇️
... and 68 more

📣 Codecov can now indicate which changes are the most critical in Pull Requests. Learn more