class_docstr: Stop the optimization when ``|x1 - x2| < delta``
  
  If the last two positions at which the objective has been evaluated
  are less than `delta` apart stop the optimization procedure.
class_docstr_tok: ["Stop","the","optimization","when","``","|x1","-","x2|","<","delta","``","If","the","last","two","positions","at","which","the","objective","has","been","evaluated","are","less","than","`","delta","`","apart","stop","the","optimization","procedure","."]
code: def _criterion(self, result):
      if len(result.x_iters) >= 2:
          return (
              result.space.distance(
                  result.x_iters[-2], result.x_iters[-1]
              )
              < self.delta
          )
  
      else:
          return None
  
imports: from time import time
  import numpy
  from guild._skopt.utils import dump
label_desc: Use image node_id 2 for calling the DeltaXStopper obj's underlying member method code with example usage: obj._criterion(result) and returns: unknown, None