riemann roch basis

edit

i have a question with this code (i speak little english)

F.<w>=GF(4,'w')
R.<X,Y,Z> = ProjectiveSpace(F,2)
C = Curve(X^2*Y + w*Y^2*Z+ w^2*Z^2*X)
print C.genus()
pts = C.rational_points()
print pts[4]
print pts[5]
D = C.divisor([ (2, pts[4]),(1, pts[5]) ])
print D
print C.riemann_roch_basis(D)

result:

(1 : w : 1)
(w : 1 : 1)
2*(X + Z, Y + (w)*Z) + (X + (w)*Z, Y + Z)
Traceback (most recent call last):    print pts[5]
  File "", line 1, in <module>

  File "/tmp/tmpvyK2s4/___code___.py", line 12, in <module>
    exec compile(u'print C.riemann_roch_basis(D)
  File "", line 1, in <module>

  File "parent.pyx", line 871, in sage.structure.parent.Parent.__getattr__ (sage/structure/parent.c:6648)
AttributeError: 'ProjectiveCurve_finite_field' object has no attribute 'riemann_roch_basis'

why?