[QUESTION] why in chapter 4 code example in colab A is not Identity matrix?

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**Describe what is unclear to you**
Hi
for the closed form of regularization in regression Equation 4-9 is discussed in the book
it is mentioned that A is an identity matrix
there is one part in the Colab of the chapter for the closed form but A is defined as [0, 0][0, 1].
Is there any special reason for that or am I missing something
I saw the np.ones is used for X_b
but I still don't get why A is not defined as [1, 0][0,1]

**To Reproduce**
If the question relates to a specific piece of code, please copy the code that fails here, using code blocks like this:

```python
alpha = 0.1
A = np.array([[0., 0.], [0., 1.]])
X_b = np.c_[np.ones(m), X]
np.linalg.inv(X_b.T @ X_b + alpha * A) @ X_b.T @ y
```

**Expected behavior**
If applicable, a clear and concise description of what you expected to happen.

**Screenshots**