docstr: global best
  :return:
docstr_tok: ["global","best",":","return",":"]
code: def update_gbest(self):
      """
      global best
      :return:
      """
      idx_min = self.pbest_y.argmin()
      if self.gbest_y > self.pbest_y[idx_min]:
          self.gbest_x = self.X[idx_min, :].copy()
          self.gbest_y = self.pbest_y[idx_min]
  
imports: import numpy
  from sko.tools import func_transformer
  from .base import SkoBase
  from .operators import crossover, mutation, ranking, selection
  from .operators import mutation
label_desc: Use image node_id 7 for calling the PSO_TSP obj's underlying member method code with example usage: obj.update_gbest() without return types