docs: def convert_units(self, from_units, to_units):
          '''
          Convert the mesh from one set of units to another.
  
          These calls are equivalent:
  
          - mesh.convert_units(from_units='cm', to_units='m')
          - mesh.scale(.01)
  
          '''
          from blmath import units
          factor = units.factor(
              from_units=from_units,
              to_units=to_units,
              units_class='length'
          )
          self.scale(factor)