docs: def geo_bounding_box(cls, field, top_left, bottom_right):
          '''
          http://www.elasticsearch.org/guide/reference/query-dsl/geo-bounding-box-filter.html
  
          > bounds = ElasticFilter().geo_bounding_box('pin.location', [40.73, -74.1], [40.717, -73.99])
          > bounds = ElasticFilter().geo_bounding_box('pin.location', dict(lat=40.73, lon=-74.1), dict(lat=40.717, lon=-73.99))
          > bounds = ElasticFilter().geo_bounding_box('pin.location', "40.73, -74.1", "40.717, -73.99")
          And geohash
          > bounds = ElasticFilter().geo_bounding_box('pin.location', "drm3btev3e86", "drm3btev3e86")
  
          '''
          return cls(geo_bounding_box={field: {'top_left': top_left, 'bottom_right': bottom_right}})