code: def __calc_z_alpha(alpha):
      """Calculate inverse of cdf of standard normal (quantile function)."""
      return 2**0.5 * sp.special.erfinv(2 * alpha - 1)
  
file_path: dipy/dipy/boots/resampling.py
imports: import numpy
  import scipy
  import warnings
label_desc: Use image node_id 4 for calling a global function with example usage: __calc_z_alpha(alpha) and returns: unknown