docs: def get_value(self, key, default=None):
          """
          Reads value from QSettings
          :param key: value key
          :param default: default value.
          :return: value
          """
          def unique(seq, idfun=None):
              if idfun is None:
                  def idfun(x):
                      return x
              # order preserving
              seen = {}
              result = []
              for item in seq:
                  marker = idfun(item)
                  if marker in seen:
                      continue
                  seen[marker] = 1
                  result.append(item)
              return result
          lst = self._settings.value('recent_files/%s' % key, default)
          # emtpy list
          if lst is None:
              lst = []
          # single file
          if isinstance(lst, str):
              lst = [lst]
          return unique([os.path.normpath(pth) for pth in lst])