docs: def check_appt(self, complex: str, house: str, appt: str) -> bool:
          """
          Check if given appartment exists in the rumetr database
          """
          self.check_house(complex, house)
          if '%s__%s__%s' % (complex, house, appt) in self._checked_appts:
              return True
  
          try:
              self.get('developers/{developer}/complexes/{complex}/houses/{house}/appts/{appt}'.format(
                  developer=self.developer,
                  complex=complex,
                  house=house,
                  appt=appt,
              ))
          except exceptions.Rumetr404Exception:
              raise exceptions.RumetrApptNotFound('Unknown appt (house is known) — may be you should create one?')
  
          self._checked_appts.add('%s__%s__%s' % (complex, house, appt))
          return True