Fix 'ModuleNotFoundError: No module named 'pypdf'' when running samp…

[th3coop]

Was taking this module for a trial run and found the sample code wasn't working. PR to resolve the error.

Repro:

• run the recommend command from the repo root python3 ./samplecode/basic_features.py
• get the following error:

 > python  .\samplecode\basic_features.py
Traceback (most recent call last):
  File ".\samplecode\basic_features.py", line 11, in <module>
    from pypdf.pdf import PdfFileReader, PdfFileWriter
ModuleNotFoundError: No module named 'pypdf'