code: def distance_to(self, address, measure="Miles", httpclient=None):
          
          if isinstance(address, Address) and self.latlng and address.latlng:
              lat1, lon1 = map(float, self.latlng)
              lat2, lon2 = map(float, address.latlng)
          elif self.latlng and type(address) is tuple:
              lat1, lon1 = map(float, self.latlng)
              lat2, lon2 = address
          else:
              raise ValueError(":address must be type tuple or Address")
              
          radius = 6371 # km          
          dlat = math.radians(lat2 - lat1)
          dlon = math.radians(lon2 - lon1)
          a = math.sin(dlat / 2) * math.sin(dlat / 2) + math.cos(math.radians(lat1)) \
            * math.cos(math.radians(lat2)) * math.sin(dlon / 2) * math.sin(dlon / 2)
          c = 2 * math.atan2(math.sqrt(a), math.sqrt(1 - a))
          d = radius * c
          # d is in kilometers
          if measure == self.KILOMETERS:
              return d
          elif measure == self.METERS:
              return d / 1000
          elif measure == self.MILES:
              return d * .621371
          else:
              return d
docs: Distance to another address