class_docstr: A PIO class, inherited from Optimizer.
  
  This is the designed class to define PIO-related
  variables and methods.
  
  References:
      H. Duan and P. Qiao.
      Pigeon-inspired optimization:a new swarm intelligence optimizerfor air robot path planning.
      International Journal of IntelligentComputing and Cybernetics (2014).
class_docstr_tok: ["A","PIO","class",",","inherited","from","Optimizer",".","This","is","the","designed","class","to","define","PIO-related","variables","and","methods",".","References",":","H.","Duan","and","P.","Qiao",".","Pigeon-inspired","optimization",":","a","new","swarm","intelligence","optimizerfor","air","robot","path","planning",".","International","Journal","of","IntelligentComputing","and","Cybernetics","(","2014",")","."]
docstr: Number of landmark iterations.
docstr_tok: ["Number","of","landmark","iterations","."]
code: def n_c2(self) -> int:
      """Number of landmark iterations."""
  
      return self._n_c2
  
imports: from typing import Any, Dict, List, Optional
  import numpy
  import opytimizer.math.random
  import opytimizer.utils.constant
  import opytimizer.utils.exception
  from opytimizer.core import Optimizer
  from opytimizer.core.agent import Agent
  from opytimizer.core.space import Space
  from opytimizer.utils import logging
label_desc: Use image node_id 4 for calling the PIO obj's underlying member method code with example usage: obj.n_c2() and returns: self