How i can print backend linear algebra?

Linear Algebra
1

I use:
print(parameters.linear_algebra_backend
And i have this error:

AttributeError Traceback (most recent call last)
in
1 from fenics import *
----> 2 print(parameters.linear_algebra_backend)

AttributeError: ‘dolfin.cpp.parameter.GlobalParameters’ object has no attribute ‘linear_algebra_backend’

This code taken from tutorial:
https://fenicsproject.org/pub/tutorial/html/._ftut1017.html#ftut:app:solver:prec

2 
from dolfin import *
print(parameters["linear_algebra_backend"])

as indicated by a quick source in the bitbucket repository:
https://bitbucket.org/search?q=repo%3Adolfin%20linear_algebra_backend&account={795b0eed-436d-4242-83d7-a46a0b061354}