fix issue with missing unit conversion in h_px and h_tx

• fix issue with missing unit conversion in h_px and h_tx
• add tests for fixed bugs
• fix error in demo script
• add new demos based on the work of @stu314159
• improve code readability by using additional tools:
  -- enforce code styling with black
  -- reduce minimal python version to 3.4 based on report from vermin
  -- fix more spelling mistakes with codespell

break out of infinite loop

v0.4.8

prep release v0.4.8

fix problem with setup.py

v0.4.7

Release 0.4.7

Version 0.4.6

Fix bugs in new functions, clean up code and introduce GitHub workflows