docs: def predict_body_units(self):
          '''
          There is no prediction for united states unit system.
          This may fail when a mesh is not axis-aligned
          '''
          longest_dist = np.max(np.max(self.v, axis=0) - np.min(self.v, axis=0))
          if round(longest_dist / 1000) > 0:
              return 'mm'
          if round(longest_dist / 100) > 0:
              return 'cm'
          if round(longest_dist / 10) > 0:
              return 'dm'
          return 'm'