code: def testSgdNestedTuple(self):
      def loss(xyz):
          x, (y, z) = xyz
          return sum(jnp.dot(a, a) for a in [x, y, z])
  
      x0 = (jnp.ones(2), (jnp.ones(2), jnp.ones(2)))
      num_iters = 100
      step_size = 0.1
      self._CheckOptimizer(
          optimizers.sgd, loss, x0, num_iters, step_size
      )
  
imports: import functools
  from absl.testing import absltest
  import numpy
  import jax.numpy
  import jax._src.test_util
  from jax import jit, grad, jacfwd, jacrev
  from jax import tree_util
  from jax import lax
  from jax.example_libraries import optimizers
  from jax import config
label_desc: Use image node_id 6 for calling the OptimizerTests obj's underlying member method code with example usage: obj.testSgdNestedTuple() and returns: sum