text: Title: SyntaxWarnings
  Body: While running an `apt upgrade` I noticed:
  
  ```
  /usr/lib/python3/dist-packages/pyqtgraph/examples/SpinBox.py:38: SyntaxWarning: invalid escape sequence '\$'
    regex='\$?(?P<number>(-?\d+(\.\d+)?)|(-?\.\d+))$')),
  ```
  
  The `\$` should be written `\\$` or `r'\$'` since a few Python releases (same for all backslash escape that have no meanings). I don't have the time to search for other occurrences of this fact, but running the tests with `PYTHONDEVMODE=1` should help spotting them :)