code: def _sigmoid(t, copy=True):
      """Return 1 / (1 + np.exp(-t))."""
      if copy:
          t = np.copy(t)
      t *= -1.0
      t = np.exp(t, t)
      t += 1.0
      t = np.reciprocal(t, t)
      return t
  
file_path: nilearn/nilearn/decoding/_objective_functions.py
imports: from functools import partial
  import numpy
  from scipy import linalg
label_desc: Use image node_id 7 for calling a global function with example usage: _sigmoid(t, copy) and returns: t