code: def save(self, filename):
      with open(filename + ".npy", "wb") as f:
          for par in get_parameters(self):
              # if par.requires_grad:
              np.save(f, par.numpy())
  
imports: import sys
  import numpy
  from tinygrad.nn.state import get_parameters
  from tinygrad.tensor import Tensor
  from tinygrad.nn import BatchNorm2d, optim
  from tinygrad.helpers import getenv
  from extra.datasets import fetch_mnist
  from extra.augment import augment_img
  from extra.training import train, evaluate
label_desc: Use image node_id 3 for calling the BigConvNet obj's underlying member method code with example usage: obj.save(filename) without return types