code: def active_vectors_info(self):
          
          if not hasattr(self, '_active_vectors_info'):
              self._active_vectors_info = [POINT_DATA_FIELD, None] # field and name
          _, name = self._active_vectors_info
  
          # rare error where scalar name isn't a valid scalar
          if name not in self.point_arrays:
              if name not in self.cell_arrays:
                  name = None
  
          return self._active_vectors_info
docs: Return the active scalar's field and name: [field, name]