The formula in the function is not giving the correct value

[quest]

Here is my function

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def coefficients(_list,q_number):     paulis = list(product([i,x,y,z],repeat=q_number))     spaulis = list(product(['i','x','y','z'],repeat=q_number))     #print(spaulis)     result = []     for k_index,kraus in enumerate(_list,start=0):         print(kraus)         for index, pauli in enumerate(paulis, start=0):             a = 1/2*(np.trace(np.matmul(kraus,pauli)))             result.append((a,spaulis[index],k_index))     return result

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i = np.array([[1, 0], [0, 1]]) x = np.array([[0, 1], [1, 0]]) y = np.array([[0,-1j],[1j,0]]) z = np.array([[1, 0], [0,-1]])

Here is my example list:

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krausf=np.array([[[-9.84447177e-01-7.67061139e-18j,           1.00575460e-03+1.82351449e-02j],         [-1.08968355e-03+6.25615662e-03j,          -9.78901978e-01-9.19498996e-03j]]]

The formula is a = 1/2*(np.trace(np.matmul(kraus,pauli))), let'stake pauli=i
I should find these result for i:
(-0.9816745775-0.004597494980000004j)
However, I am finding:
[-0.49222359-3.83530569e-18j, 0.00050288+9.11757245e-03j] from function. I can't see the point that I missed

What is happening?

[quest]

This line a = 1/2*(np.trace(np.matmul(kraus,pauli))) should be a = 1/2*(np.trace(np.matmul(kraus,pauli[0])))