code: def psi(self, t, s):
      return np.sqrt(np.exp((self.log_alpha(t) - self.log_alpha(s))))
  
file_path: diffusion-for-beginners/samplers/exponential_integrator.py
imports: import torch
  import numpy
label_desc: Use image node_id 4 for calling the ExponentialSampler obj's underlying member method code with example usage: obj.psi(t, s) and returns: np