message: Add usage example to tf.nn.conv2d()
diff: @@ -1884,6 +1884,14 @@ def conv2d_v2(input, # pylint: disable=redefined-builtin
  Must have `strides[0] = strides[3] = 1`. For the most common case of the same
  horizontal and vertices strides, `strides = [1, stride, stride, 1]`.
  + Usage Example:
  + >>> kernel_in = np.array([
  + ... [ [[2, 0.1]],[[3, 0.2]] ],
  + ... [ [[0, 0.3]],[[1, 0.4]] ]])
  + >>> x = tf.placeholder(tf.float32, shape=[1, 5, 5, 1])
  + >>> kernel = tf.constant(kernel_in, dtype=tf.float32)
  + <tf.Tensor 'Conv2D_1:0' shape=(1, 4, 4, 2) dtype=float32>
  +
  Args:
  input: A `Tensor`. Must be one of the following types:
  `half`, `bfloat16`, `float32`, `float64`.
  