A 4x4 transformation matrix based on api Matrix
>>> from pymel.all import *
>>> import pymel.core.datatypes as dt
>>>
>>> i = dt.Matrix()
>>> print i.formated()
[[1.0, 0.0, 0.0, 0.0],
[0.0, 1.0, 0.0, 0.0],
[0.0, 0.0, 1.0, 0.0],
[0.0, 0.0, 0.0, 1.0]]
>>> v = dt.Matrix(1, 2, 3)
>>> print v.formated()
[[1.0, 2.0, 3.0, 0.0],
[1.0, 2.0, 3.0, 0.0],
[1.0, 2.0, 3.0, 0.0],
[1.0, 2.0, 3.0, 0.0]]