code: def pso_add(self, c, x1, x2):
      x1, x2 = x1.tolist(), x2.tolist()
      ind1, ind2 = np.random.randint(0, self.n_dim - 1, 2)
      if ind1 >= ind2:
          ind1, ind2 = ind2, ind1 + 1
  
      part1 = x2[ind1:ind2]
      part2 = [i for i in x1 if i not in part1]  # this is very slow
  
      return np.array(part1 + part2)
  
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 3 for calling the PSO_TSP obj's underlying member method code with example usage: obj.pso_add(c, x1, x2) and returns: np