code: def create_mod_site(self, mc):
          
          site_name = get_mod_site_name(mc)
          (unmod_site_state, mod_site_state) = states[mc.mod_type]
          self.create_site(site_name, (unmod_site_state, mod_site_state))
          site_anns = [Annotation((site_name, mod_site_state), mc.mod_type,
                                  'is_modification')]
          if mc.residue:
              site_anns.append(Annotation(site_name, mc.residue, 'is_residue'))
          if mc.position:
              site_anns.append(Annotation(site_name, mc.position, 'is_position'))
          self.site_annotations += site_anns
docs: Create modification site for the BaseAgent from a ModCondition.