docstr: Helper method for the sigmoid function
  
  Parameters
  ----------
  x : numpy.ndarray
      Input vector for sigmoid computation
  
  Returns
  -------
  numpy.ndarray
      Output sigmoid computation
docstr_tok: ["Helper","method","for","the","sigmoid","function","Parameters","--","--","--","--","--","x",":","numpy.ndarray","Input","vector","for","sigmoid","computation","Returns","--","--","--","-","numpy.ndarray","Output","sigmoid","computation"]
code: def _sigmoid(self, x):
      """Helper method for the sigmoid function
  
      Parameters
      ----------
      x : numpy.ndarray
          Input vector for sigmoid computation
  
      Returns
      -------
      numpy.ndarray
          Output sigmoid computation
      """
      return 1 / (1 + np.exp(-x))
  
file_path: pyswarms/pyswarms/discrete/binary.py
imports: import logging
  import numpy
  import multiprocessing
  from collections import deque
  from ..backend.operators import compute_pbest, compute_objective_function
  from ..backend.topology import Ring
  from ..backend.handlers import BoundaryHandler, VelocityHandler
  from ..base import DiscreteSwarmOptimizer
  from ..utils.reporter import Reporter
label_desc: Use image node_id 4 for calling the BinaryPSO obj's underlying member method code with example usage: obj._sigmoid(x) and returns: unknown