Command matrix() not work, but worked before
coeff = matrix(QQ, [[-7, -6, -12], [5, 5, 7], [1, 0, 4]])
NameError Traceback (most recent call last) Cell In[1], line 1 ----> 1 coeff = matrix(QQ, [[-7, -6, -12], 2 [5, 5, 7], 3 [1, 0, 4]])
NameError: name 'matrix' is not defined
What to do?