matrix

How do I create matrix type (or object) in python?
I’d like to use setMatrix() method for Mesh Object.
I tried 4*4 list as an input but it gave me the error message of:
expected matrix object as argument

Thanks in advance

from Blender.Mathutils import *
m1 = Matrix()
rowA = [1,2,3]
rowB = [4,5,6]
rowC = [7,8,9]
m2 = Matrix(rowA, rowB, rowC)