docs: def addfield(self, name, type, width=10):
          """
          add a field to the vector layer
  
          Parameters
          ----------
          name: str
              the field name
          type: int
              the OGR Field Type (OFT), e.g. ogr.OFTString.
              See `Module ogr <https://gdal.org/python/osgeo.ogr-module.html>`_.
          width: int
              the width of the new field (only for ogr.OFTString fields)
  
          Returns
          -------
  
          """
          fieldDefn = ogr.FieldDefn(name, type)
          if type == ogr.OFTString:
              fieldDefn.SetWidth(width)
          self.layer.CreateField(fieldDefn)