以下代码用于矩阵与其转置矩阵相乘：

import numpy as np

def multiply_At_A(A):
    dim1 = A.shape[0]
    dim2 = A.shape[1]
    matrix = np.zeros([dim2,dim2])
    
    for i in range(dim2):
        for j in range(dim2):
            for k in range(dim1):
                matrix[i,j]==A[i,k]*A[k,j]
        return matrix
    A=np.array([[1,2,3],[4,5,6],[7,8,9]])
    print(matrix)

我应该得到一个结果，但我没有得到任何结果