Example in python docs doesn't work

[domoritz]

In https://potassco.org/clingo/python-api/current/clingo.html#Control-solve

#script (python)
import clingo
 
def main(prg):
    prg.add("p", "{a;b;c}.")
    prg.ground([("p", [])])
    ret = prg.solve()
    print(ret)
 
#end.

Doesn't work because add expects more arguments.