code: def set_password(self, service, username, password):
          
          password = self._encrypt(password or '')
          keyring_working_copy = copy.deepcopy(self._keyring)
          service_entries = keyring_working_copy.get(service)
          if not service_entries:
              service_entries = {}
              keyring_working_copy[service] = service_entries
          service_entries[username] = password
          save_result = self._save_keyring(keyring_working_copy)
          if save_result == self.OK:
              self._keyring_dict = keyring_working_copy
              return
          elif save_result == self.CONFLICT:
              # check if we can avoid updating
              self.docs_entry, keyring_dict = self._read()
              existing_pwd = self._get_entry(self._keyring, service, username)
              conflicting_pwd = self._get_entry(keyring_dict, service, username)
              if conflicting_pwd == password:
                  # if someone else updated it to the same value then we are done
                  self._keyring_dict = keyring_working_copy
                  return
              elif conflicting_pwd is None or conflicting_pwd == existing_pwd:
                  # if doesn't already exist or is unchanged then update it
                  new_service_entries = keyring_dict.get(service, {})
                  new_service_entries[username] = password
                  keyring_dict[service] = new_service_entries
                  save_result = self._save_keyring(keyring_dict)
                  if save_result == self.OK:
                      self._keyring_dict = keyring_dict
                      return
                  else:
                      raise errors.PasswordSetError(
                          'Failed write after conflict detected')
              else:
                  raise errors.PasswordSetError(
                      'Conflict detected, service:%s and username:%s was '
                      'set to a different value by someone else' % (
                          service,
                          username,
                      ),
                  )
  
          raise errors.PasswordSetError('Could not save keyring')
docs: Set password for the username of the service