def METHOD_NAME(self):
    heteroatoms = self.extractor.get_heteroatoms()
    special_cs = self.extractor.get_special_carbon()
    link = self.extractor.link_marked_atoms(heteroatoms | special_cs)
    assert len(link) == 1
    assert len(link[0]) == 9
    # Exclude Oxygen-related functional groups
    heteroatoms_no_o = self.extractor.get_heteroatoms(elements=["N"])
    special_cs_no_o = self.extractor.get_special_carbon(elements=["N"])
    all_marked = heteroatoms_no_o | special_cs_no_o
    link_no_o = self.extractor.link_marked_atoms(all_marked)
    assert len(link_no_o) == 2