Find Topocentric RA & Dec from Geocentric ICRF Vector

[randyg3000]

Hello,
If I have a Geocentric ICRF Vector how might I use skyfield to get a Topocentric RA & Dec?.

I can build an ICRF vector as such:

icrf_vector = ICRF(
t=t,
position_au=Distance(km=[icrf_x, icrf_y, icrf_z]).au,
velocity_au_per_d=Velocity(
km_per_s=[icrf_vx, icrf_vy, icrf_vz]
).au_per_d,
)

and get a geocentric ra/dec easily:

ra, dec, distance = icrf_vector.radec(epoch="date")

However the requirement is to get a Topocentric RA/Dec and I don't see how to find (or "observe") the topocentric RA/Dec from a given point on earth. Thanks in advance for any help.