code: def y_exact(self, t):
      return (
          -0.5 * t**4 * torch.cos(2 * t)
          + 0.5 * t**3 * torch.sin(2 * t)
          + 0.25 * t**2 * torch.cos(2 * t)
          - t**3
          + 2 * t**4
          + (math.pi - 0.25) * t**2
      )
  
file_path: torchdiffeq/tests/problems.py
imports: import math
  import numpy
  import scipy.linalg
  import torch
label_desc: Use image node_id 2 for calling the SineODE obj's underlying member method code with example usage: obj.y_exact(t) and returns: unknown