code: def backward(
      self, grad_output: LazyBuffer
  ) -> Tuple[Optional[LazyBuffer], Optional[LazyBuffer]]:
      denom = (self.a.e(BinaryOps.MUL, self.a)).e(
          BinaryOps.ADD, self.b.e(BinaryOps.MUL, self.b)
      )
      return (
          grad_output.e(BinaryOps.MUL, self.b.e(BinaryOps.DIV, denom))
          if self.needs_input_grad[0]
          else None,
          grad_output.e(
              BinaryOps.MUL,
              self.a.const(0)
              .e(BinaryOps.SUB, self.a)
              .e(BinaryOps.DIV, denom),
          )
          if self.needs_input_grad[1]
          else None,
      )
  
imports: import unittest
  import numpy
  from typing import Optional, Tuple
  from tinygrad.helpers import prod
  from tinygrad.dtype import dtypes
  from tinygrad.lazy import Buffer, create_lazybuffer
  from tinygrad.device import CompiledASTRunner, Device
  from tinygrad.shape.shapetracker import ShapeTracker
  from tinygrad.ops import LoadOps, BinaryOps
  from tinygrad.lazy import LazyBuffer
  from tinygrad.tensor import Function
  from tinygrad.tensor import Tensor
label_desc: Use image node_id 2 for calling the ATan2 obj's underlying member method code with example usage: obj.backward(grad_output) and returns: unknown,  unknown