Hello yourvick,
Please check the commands below:
sensor = chunk.sensors[0]
sensor.film_camera = True #switches the sensor to film camera with fiducial marks
f = chunk.addMarker()
f.type = Metashape.Marker.Type.Fiducial #switches marker type to fiducial
f.sensor = sensor #assigns fiducial to the sensor
f.reference.location = Metashape.Vector([120.22, 122.15, 1]) #coordinates in mm
f.projections[camera] = Metashape.Marker.Projection(Vector([89.49, 67.35]), True) #coordinates in pix
If there are more specific questions, please let me know.