NeuralNetwork - Display matrix with colors (BUG)

import numpy
a = numpy.zeros( [3,2] )
a[0,0] = 1
a[0,1] = 2
a[1,0] = 9
a[2,1] = 12
print(a)

import matplotlib.pyplot
%matplotlib inline
matplotlib.pyplot.imshow(a, interpolation="nearest")
<matplotlib.image.AxesImage at 0x108917710>