### import sage.rings.polynomial.multi_polynomial_sequence

Hi all:

I'm writing some new Sage code to do partial fraction decompositions of
multivariate rational expressions and want to use the Sequence() and
algebraic_dependence() methods from
sage.rings.polynomial.multi_polynomial_sequence. What's the best
import call to use?

I've played around with various import calls, and most recently ~~tried~~tried the following from within the function i'm writing.

```
from sage.structure.sequence import *
from sage.rings.polynomial.polynomial_ring_constructor import *
from sage.rings.polynomial.multi_polynomial_sequence import *
```

~~which i ~~I thought that would work and be overkill, but i got the error message

```
/Applications/sage/local/lib/python2.6/site-packages/sage/rings/polynomial/multi_polynomial_sequence.pyc
in algebraic_dependence(self)
600 T = T+'T'
601 Ts = [T + str(j) for j in range(r)]
--> 602 RR = PolynomialRing(K,d+r,tuple(Xs+Ts))
603 Vs = list(RR.gens())
604 Xs = Vs[0 :d]
NameError: global name 'PolynomialRing' is not defined
```

Any advice on this particular import or imports in general would be appreciated.

Thanks.