Python: SyntaxError: keyword can't be an expression

In a Python script I call a function from rpy2, but I get this error:

#using an R module 
res = DirichletReg.ddirichlet(np.asarray(my_values),alphas,
                              log=False, sum.up=False) 
SyntaxError: keyword can't be an expression

What exactly went wrong here?