docs: def _get_col_epsg(mapped_class, geom_attr):
      """Get the EPSG code associated with a geometry attribute.
  
      Arguments:
  
  
      geom_attr
          the key of the geometry property as defined in the SQLAlchemy
          mapper. If you use ``declarative_base`` this is the name of
          the geometry attribute as defined in the mapped class.
      """
      col = class_mapper(mapped_class).get_property(geom_attr).columns[0]
      return col.type.srid