dir .... often uncovers the unincluded
proj = r"C:\arcpro_npg\npg\Project_npg\npGeom.aprx"
aprx = arcpy.mp.ArcGISProject(proj)
dir(aprx)
['__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__',
'__format__', '__from_scripting_arc_object__', '__ge__', '__getattribute__',
'__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__',
'__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__',
'__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__',
'__weakref__', '_arc_object',
'activeMap',
'activeView',
'dateSaved',
'defaultGeodatabase',
'defaultToolbox',
'documentVersion',
'filePath',
'homeFolder',
'importDocument',
'listBrokenDataSources',
'listColorRamps',
'listLayouts',
'listMaps',
'listReports',
'metadata',
'save',
'saveACopy',
'updateConnectionProperties']
.... help on those properties and methods is quite limited though
print(aprx.save.__doc__)
ArcGISProject.save()
Saves changes to an ArcGISProject ( .aprx ).
... sort of retired...