How can one find an integral basis of Q-vector space of cuspidal holomorphic modular forms of level Γ0(p) and weight 2 that have Fourier coefficients in Q? Suchs forms are automatically newforms (because there are no holomorphic modular forms of level 1 and weight 2).
I am able to find a basis for the space of all cuspidal holomorphic modular forms of level Γ0(p) and weight 2 (including those that have non-rational Fourier coefficients) using Newforms(Gamma0(p), 2, names="a")
but I do not see how to get what I need from that.