Pyqgis code for generating themes for each layer group

Question

Based on

https://gis.stackexchange.com/questions/428662/how-to-add-a-layer-to-a-maptheme-in-qgis-with-pyqgis

and

https://gis.stackexchange.com/questions/364733/automatically-creating-themes-in-qgis-3-x

I wrote two Pyqgis codes for generating themes for each layer group. Both are not working.

Which one shows a possible solution and were is the mistake (2 is my favorite)?

1.

root = QgsProject.instance().layerTreeRoot()
groups = root.findGroups()

for group in groups:
       group.setItemVisibilityChecked(True)
       layersToChanges = group.findLayers()
       for layer in layersToChanges:
    for child in root.children():
        if isinstance(child, QgsLayerTreeGroup):
            print("- group: " + child.name())
        elif isinstance(child, QgsLayerTreeLayer):
            print("- layer: " + child.name() + "  ID: " + child.layerId())
            # Layer you want to tick
            if (child.name() == layer):
                child.setItemVisibilityChecked(True)
                print("Check only once")
            elif child.name() in layersToChanges:
                child.setItemVisibilityChecked(False)
                print("Check the others you want to hide")
    mapThemeRecord = QgsMapThemeCollection.createThemeFromCurrentState(
        QgsProject.instance().layerTreeRoot(),
        iface.layerTreeView().layerTreeModel()
    )
    mapThemesCollection.insert(layer, mapThemeRecord)

2.EDIT:

#Variables: Groups, project layer
root = QgsProject.instance().layerTreeRoot()
groups = root.findGroups()
AllLayers = root.findLayers()

#Visibilities
for layer in AllLayers:
    layer.setItemVisibilityChecked(False)
for group in groups:
    group.setItemVisibilityChecked(False)

for group in groups:
    group.setItemVisibilityChecked(True)
    groupLayers = group.findLayers()
    for groupLayer in groupLayers:
        groupLayer.setItemVisibilityChecked(True)

#Set themes for each group
    mtc = QgsProject.instance().mapThemeCollection()
    theme_name = str(group)
    theme_state = mtc.mapThemeState(theme_name)
    layer_record = QgsMapThemeCollection.MapThemeLayerRecord()
    theme_state.addLayerRecord(layer_record)
    group.setItemVisibilityChecked(False)

Answer 1

This made it:

#Variables: Groups, project layer
root = QgsProject.instance().layerTreeRoot()
groups = root.findGroups()
AllLayers = root.findLayers()
mapThemesCollection = QgsProject.instance().mapThemeCollection()

#Visibilities
for layer in AllLayers:
    layer.setItemVisibilityChecked(False)
for group in groups:
    group.setItemVisibilityChecked(False)

for group in groups:
    group.setItemVisibilityChecked(True)
    groupLayers = group.findLayers()
    for groupLayer in groupLayers:
        groupLayer.setItemVisibilityChecked(True)
#Set themes for each group
    mapThemeRecord = QgsMapThemeCollection.createThemeFromCurrentState(
    QgsProject.instance().layerTreeRoot(),
    iface.layerTreeView().layerTreeModel())
    mapThemesCollection.insert(str(group), mapThemeRecord)