Downgrade to PySide2

Debian stable does not have PySide6 packaged and PySide2's API is
similar enough.

birdvisu/visualisation/annotators.py

@@ -8,7 +8,7 @@ from enum import Enum, auto
 from dataclasses import dataclass
 import re
 import random
-from PySide6 import QtCore, QtGui, QtWidgets
+from PySide2 import QtCore, QtGui, QtWidgets
 
 # Classification
 

poor_mans_visualisation.py

@@ -30,7 +30,7 @@ final_topo = combiner.get_complete_topology()
 from birdvisu.visualisation import annotators
 
 # annotators.create_qgritems does not like being run without Qt initialization.
-from PySide6 import QtCore, QtGui, QtWidgets
+from PySide2 import QtCore, QtGui, QtWidgets
 app = QtWidgets.QApplication([])
 
 annotated_topology = maps_new.annotate_topology(final_topo,
@@ -62,4 +62,4 @@ for tagsrc in [
 view = QtWidgets.QGraphicsView(scene)
 view.show()
 
-app.exec()
+app.exec_()

snippets/qt_graphics.py

@@ -1,6 +1,6 @@
 #!/usr/bin/env python3
 
-from PySide6 import QtCore, QtGui, QtWidgets
+from PySide2 import QtCore, QtGui, QtWidgets
 
 
 class Window(QtWidgets.QWidget):