def get_uniq_atoms(atom: Atom) -> set[Atom]:
"""Return the set of all unique atoms in atom."""
result = {atom}
# Recursive cases
if atom.is_link():
for o in atom.out:
result.update(get_uniq_atoms(o))
return result
# Base cases (atom is a node)
return result
def is_empty_link(atom: Atom) -> bool:
"""Return True iff the atom is a link with empty outgoing set."""
return atom.is_link() and atom.out == []