code: def test_initialize_lengthscale_batch(self):
      kernel = RBFKernelGrad(batch_shape=torch.Size([2]))
      ls_init = torch.tensor([3.14, 4.13])
      kernel.initialize(lengthscale=ls_init)
      actual_value = ls_init.view_as(kernel.lengthscale)
      self.assertLess(
          torch.norm(kernel.lengthscale - actual_value), 1e-5
      )
  
file_path: gpytorch/test/kernels/test_rbf_kernel_grad.py
imports: import unittest
  import torch
  from gpytorch.kernels import RBFKernelGrad
  from gpytorch.test.base_kernel_test_case import BaseKernelTestCase
label_desc: Use image node_id 7 for calling the TestRBFKernelGrad obj's underlying member method code with example usage: obj.test_initialize_lengthscale_batch() without return types