docs: def prep_search_string(self, search_string, add_wildcards=False):
      """Prepares search string as a proper whoosh search string.
  
      Args:
        search_string (str): it prepares the search string and see if
        the lenght is correct.
  
      Optional Args:
          add_wildcards (bool): It runs a query for inexact queries.
  
      Raises:
        ValueError: When the search string does not have the appropriate
        lenght. This lenght may be changed in the config options.
      """
  
      s = search_string.strip()
      try:
        s = str(s)
      except:
        pass
      s = s.replace('*', '')
  
      if len(s) < self._pw.search_string_min_len:
        raise ValueError('Search string must have at least {} characters'
          .format(self._pw.search_string_min_len))
      if add_wildcards:
        s = '*{0}*'.format(re.sub('[\s]+', '* *', s))
      return s