code: def geo_distance(cls, field, center, distance, distance_type=None):
          '''
          http://www.elasticsearch.org/guide/reference/query-dsl/geo-distance-filter.html
          Filters documents that include only hits that exists within a specific distance from a geo point.
          field - Field name
          center - Center point (Geo point)
          distance - String for the distance
          distance_type - (arc | plane) How to compute the distance. Can either be arc (better precision) or plane (faster). Defaults to arc
          > bounds = ElasticFilter().geo_distance('pin.location', [40.73, -74.1], '300km')
          '''
  
          instance = cls(geo_distance={'distance': distance, field: center})
          if distance_type is not None:
              instance['geo_distance']['distance_type'] = distance_type
          return instancf geo_distance(cls, field, center, distance, distance_type=None):
          '''
          http://www.elasticsearch.org/guide/reference/query-dsl/geo-distance-filter.html
          Filters documents that include only hits that exists within a specific distance from a geo point.
          field - Field name
          center - Center point (Geo point)
          distance - String for the distance
          distance_type - (arc | plane) How to compute the distance. Can either be arc (better precision) or plane (faster). Defaults to arc
          > bounds = ElasticFilter().geo_distance('pin.location', [40.73, -74.1], '300km')
          '''
  
          instance = cls(geo_distance={'distance': distance, field: center})
          if distance_type is not None:
              instance['geo_distance']['distance_type'] = distance_type
          return instance
docs: http://www.elasticsearch.org/guide/reference/query-dsl/geo-distance-filter.html
          Filters documents that include only hits that exists within a specific distance from a geo point.
          field - Field name
          center - Center point (Geo point)
          distance - String for the distance
          distance_type - (arc | plane) How to compute the distance. Can either be arc (better precision) or plane (faster). Defaults to arc
          > bounds = ElasticFilter().geo_distance('pin.location', [40.73, -74.1], '300km')