pyqgis - removeGroup() in QGIS 3

I am updating a plugin from QGIS 2 to 3. I need to iterate through the groups (the names are dynamic) and remove them with their respective child layers. I need to get a list of groups and then iterate through the groups and delete them. The original code is as follows:

legend = self.iface.legendInterface()
group_names = legend.groups()
rev = self.groups[:]
rev.reverse()

...
    for i, group in enumerate(rev):
        legend.removeGroup(group)

I replaced self.iface.legendInterface() with QgsProject.instance().layerTreeRoot() but group_names = legend.groups() fails with the message 'QgsLayerTree' object has no attribute 'groups'

What is the proper container of the groups and how do I access the collection; and, once found, how do I delete those groups? A search for information on how to remove groups from a layer tree in QGIS 3 has proven fruitless.