I have installed numpy as following in ubuntu 14.04, but as is indicated in the sample code using matmul leads to error.

```
sudo apt-get install python3-numpy

$ python3
Python 3.4.3 (default, Oct 14 2015, 20:28:29) 
[GCC 4.8.4] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import numpy as np
>>> np.__version__
'1.8.2'
>>> a = [[1, 0], [0, 1]]
>>> b = [[4, 1], [2, 2]]
>>> np.matmul(a, b)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'module' object has no attribute 'matmul'
>>> 

```

What is my fault?   

Thanks.