basic implementation of the __geo_interface__ (Python 3)

 PyGeoIf provides a GeoJSON-like protocol for geo-spatial (GIS) vector data.
 .
 So when you want to write your own geospatial library with support for this
 protocol you may use pygeoif as a starting point and build your functionality
 on top of it
 .
 You may think of pygeoif as a ‘shapely ultralight’ which lets you construct
 geometries and perform very basic operations like reading and writing
 geometries from/to WKT, constructing line strings out of points, polygons from
 linear rings, multi polygons from polygons, etc. It was inspired by shapely and
 implements the geometries in a way that when you are familiar with shapely you
 feel right at home with pygeoif.