Append tensor x2 to the end of tensor x1.
tf.keras.ops.append(
    x1, x2, axis=None
)
| Args | 
|---|
| x1 | First input tensor. | 
| x2 | Second input tensor. | 
| axis | Axis along which tensor x2is appended to tensorx1.
IfNone, both tensors are flattened before use. | 
| Returns | 
|---|
| A tensor with the values of x2appended tox1. | 
Examples:
x1 = keras.ops.convert_to_tensor([1, 2, 3])
x2 = keras.ops.convert_to_tensor([[4, 5, 6], [7, 8, 9]])
keras.ops.append(x1, x2)
array([1, 2, 3, 4, 5, 6, 7, 8, 9], dtype=int32)
When axis is specified, x1 and x2 must have compatible shapes.
>>> x1 = keras.ops.convert_to_tensor([[1, 2, 3], [4, 5, 6]])
>>> x2 = keras.ops.convert_to_tensor([[7, 8, 9]])
>>> keras.ops.append(x1, x2, axis=0)
array([[1, 2, 3],
        [4, 5, 6],
        [7, 8, 9]], dtype=int32)
>>> x3 = keras.ops.convert_to_tensor([7, 8, 9])
>>> keras.ops.append(x1, x3, axis=0)
Traceback (most recent call last):
    ...
TypeError: Cannot concatenate arrays with different numbers of
dimensions: got (2, 3), (3,).