code: def radians_to(self, other):
          
          d2r = math.pi / 180.0
          lat1rad = self.latitude * d2r
          long1rad = self.longitude * d2r
  
          lat2rad = other.latitude * d2r
          long2rad = other.longitude * d2r
  
          delta_lat = lat1rad - lat2rad
          delta_long = long1rad - long2rad
  
          sin_delta_lat_div2 = math.sin(delta_lat / 2.0)
          sin_delta_long_div2 = math.sin(delta_long / 2.0)
  
          a = ((sin_delta_lat_div2 * sin_delta_lat_div2) +
               (math.cos(lat1rad) * math.cos(lat2rad) *
                sin_delta_long_div2 * sin_delta_long_div2))
          a = min(1.0, a)
          return 2 * math.asin(math.sqrt(a))
docs: Returns the distance from this GeoPoint to another in radians.
  
          :param other: point the other GeoPoint
          :type other: GeoPoint
          :rtype: float