[Python] Skyfield: observe x,y,z postion in ICRF

I have a satellites x,y,z coordinates in the ICRF ref. frame. I know the lat, long and altitude of my observer (wgs84). Now, using skfield I want to get the vector from my observer to the satellite such that I can find the azimuth and elevation. I want to use the observe method to take light travel time into acount.

This is what I have so far:

from skyfield.api import load, wgs84
from skyfield.positionlib import ICRF, Barycentric
import numpy as np

# Load ephemeris data
ts = load.timescale()
eph = load('de421.bsp')

# Create a time object
t = ts.utc(2023, 1, 1)
jupiter = eph['jupiter barycenter']

# Example: Converting between ICRF and Earth-centered frames


# id Name
# 0 SOLAR SYSTEM BARYCENTE
# 3 EARTH BARYCENTER
# 399 EARTH

# vector sum of 2 vectors
# SOLAR SYSTEM BARYCENTER -> EARTH BARYCENTER
# EARTH BARYCENTER -> EARTH
earth_ICRF = eph['earth']

# vector from EARTH to antenna position
# EARTH -> WGS84 latitude longitude altitude
antenna_pos_earth = wgs84.latlon(47.397490, 8.550440, 499.5) # vector sum of 0 SOLAR SYSTEM BARYCENTER -> 3 EARTH BARYCENTER -> 399 EARTH

# vector sum of 3 vectors
# SOLAR SYSTEM BARYCENTER -> EARTH BARYCENTER
# EARTH BARYCENTER -> EARTH
# EARTH -> WGS84 latitude longitude altitude
antenna_pos_ICRF = earth_ICRF + antenna_pos_earth



# spacecraft ICRF coordinates in km and km/s
x, y, z = 1000.0, 2000.0, 3000.0 # position in km
vx, vy, vz = 1.0, 2.0, 3.0 # velocity in km/s

# Create position vector (convert from km to au)
position_au = np.array([x, y, z]) / 149597870.7 # Convert km to au
velocity_au_per_day = np.array([vx, vy, vz]) * 86400 / 149597870.7 # Convert km/s to au/day

position = Barycentric(position_au, velocity_au_per_day, t)

print(antenna_pos_ICRF.at(t).observe(position))


error

line 49, in <module>
print(antenna_pos_ICRF.at(t).observe(position))
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
line 690, in observe
p, v, t, light_time = body._observe_from_bcrs(self)
^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'Barycentric' object has no attribute '_observe_from_bcrs'

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