code: def within(self, lat, lon, radius):
  		'''
  		Apply a geo=$circle/$center filter. Radius is in meters. Subsequent within() 
  		calls replace earlier geo filters on this query.
  		'''
  		self._geo = { "$circle": { 
  						"$center": [
  							factual.common.shared_filter_helpers.GeoScalar(lat), 
  							factual.common.shared_filter_helpers.GeoScalar(lon), 
  							], 
  						"$meters": radius 
  						}
  					}
  		return self within(self, lat, lon, radius):
  		'''
  		Apply a geo=$circle/$center filter. Radius is in meters. Subsequent within() 
  		calls replace earlier geo filters on this query.
  		'''
  		self._geo = { "$circle": { 
  						"$center": [
  							factual.common.shared_filter_helpers.GeoScalar(lat), 
  							factual.common.shared_filter_helpers.GeoScalar(lon), 
  							], 
  						"$meters": radius 
  						}
  					}
  		return self
docs: Apply a geo=$circle/$center filter. Radius is in meters. Subsequent within() 
  		calls replace earlier geo filters on this query.