code: def _std(self, t):
      b0, b1, s = self.beta_min, self.beta_max, self.stiffness
      return (
          1 - torch.exp(-0.5 * s * t * (t * (b1 - b0) + 2 * b0))
      ) / s
  
imports: import abc
  import warnings
  import numpy
  import torch
label_desc: Use image node_id 7 for calling the OUVPSDE obj's underlying member method code with example usage: obj._std(t) and returns: unknown