https://django-mptt.readthedocs.io/en/latest/mptt.managers.html
mptt.managers — django-mptt 0.19rc1 documentation
mpttmanagersdjangodocumentation
https://www.mptt.co.uk/courses-by-category/construction-plant-courses/npors-n027-excavation-marshall-banksperson/
N027 Excavation Marshall (Banksperson) | NPORS | MPTT
NPORS N027 Excavation Marshall / Banksperson training — pedestrian-machinery interface safety on excavation sites. CSCS-recognised. Book online with MPTT.
excavationmarshallmptt