code: def trained_optimizer():
      """Returns a trained optimizer instance with 100 iterations"""
      options = {"c1": 0.5, "c2": 0.3, "w": 0.9}
      optimizer = GlobalBestPSO(
          n_particles=10, dimensions=2, options=options
      )
      optimizer.optimize(sphere, iters=100)
      return optimizer
  
file_path: pyswarms/tests/utils/plotters/conftest.py
imports: import os
  import matplotlib
  import numpy
  import pytest
  from pyswarms.single import GlobalBestPSO
  from pyswarms.utils.functions.single_obj import sphere
  from pyswarms.utils.plotters.formatters import Mesher
label_desc: Use image node_id 1 for calling a global function with example usage: trained_optimizer() and returns: optimizer