# SageMath code for working with modular form 891.2.e.q


# Compute space of new eigenforms: 
from sage.modular.dirichlet import DirichletCharacter
H = DirichletGroup(891, base_ring=CyclotomicField(6))
chi = DirichletCharacter(H, H._module([4, 0]))
N = Newforms(chi, 2, names="a")

# select newform: 
traces = [6,-1,0,-5,2,0,-7]
f = next(g for g in N if [g.coefficient(i+1).trace() for i in range(7)] == traces)

# q-expansion: 
f.q_expansion() # note that sage often uses an isomorphic number field