The "find_intersection_union_subspace" function seems to have some issues

Question

Source codes are as follows:

import numpy as np

def find_intersection_union_subspace(A, B):
    # Convert input basis vectors matrices to numpy arrays
    A = np.array(A)
    B = np.array(B)

    # Calculate the intersection of the two subspaces
    intersection = np.linalg.solve(A.T @ A, A.T) @ B
    intersection_dim = np.linalg.matrix_rank(intersection)

    # Calculate the union of the two subspaces
    union = np.hstack((A, B))
    union_dim = np.linalg.matrix_rank(union)

    return intersection, intersection_dim, union, union_dim

A = [[1, -1],
     [2, 1],
     [1, 1],
     [0,1]]

B = [[2, -1],
     [-1, -1 ],
     [0, 3],
     [0,7]]

print("Matrix of basis vectors for A:\n", A)
print("Matrix of basis vectors for B:\n", B)
dim_A = np.linalg.matrix_rank(np.array(A))
dim_B = np.linalg.matrix_rank(np.array(B))  # Correctly calculate the dimension of B
print(f"Dimension of linear subspace A: {dim_A}")
print(f"Dimension of linear subspace B: {dim_B}")
intersection, intersection_dim, union, union_dim = find_intersection_union_subspace(A, B)

print("Matrix of basis vectors for intersection:")
print(intersection)
print(f"Dimension of the intersection: {intersection_dim}")

print("\nMatrix of basis vectors for the union:")
print(union)
print(f"Dimension of the union: {union_dim}")

Output results are as follows：

Matrix of basis vectors for A:
[[1, -1], [2, 1], [1, 1], [0, 1]]
Matrix of basis vectors for B:
[[2, -1], [-1, -1], [0, 3], [0, 7]]
Dimension of linear subspace A: 2
Dimension of linear subspace B: 2
Matrix of basis vectors for the intersection:
[[ 0.3 -1. ]
[-0.9 3. ]]
Dimension of the intersection: 1

Matrix of basis vectors for the union:
[[ 1 -1 2 -1]
[ 2 1 -1 -1]
[ 1 1 0 3]
[ 0 1 0 7]]
Dimension of the union: 4

From the formula dim(A∩B) = dim(A) + dim(B) - dim(A+B), it is known that dim(A∩B) = 0. However, the dimension given here is 1. Where is the problem here? The result I obtained from manual calculation is also dim(A∩B) = 0. Is there a problem with the find_intersection_union_subspace function?