Tangent vector field

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Hello over there.

I'm trying to calculate the norm, or the norm squared, of a vector field tangent to a curve over a manifold. The examples on Curves in Manifold and Vector Fields from the documentation work fine, but when I try a tangent to a curve I get the error ValueError: the two subsets do not belong to the same manifold.

Here is my minimal example:

N = Manifold(2, 'N', latex_name=r'\mathcal{N}',structure='Lorentzian')
var('u v')
chart_N.<u,v> = N.chart()
R.<t> = RealLine()
beta = N.curve({chart_N: [t, sech(t)]}, (t,0, oo), latex_name=r'\beta')
vbeta = beta.tangent_vector_field()
g=N.metric(name='g', latex_name=r'g_{\mathcal{N}}')
g[0,0]=-1
g[1,1]=cosh(u)**2

Everything is fine until here. I got the error when I tried

g(vbeta,vbeta)

or

vbeta.norm(metric=g)

What I'm missing?

Thank you in advance.