docs: def near(self, x, y, max_distance=None):
          """ Return documents near the given point
          """
          expr = {
              self : {'$near' : [x, y]}
          }
          if max_distance is not None:
              expr[self]['$maxDistance'] = max_distance
          # if bucket_size is not None:
          #     expr['$bucketSize'] = max_distance
          return QueryExpression(expr)