docs: def _is_valid_string(self, inpt, metadata):
          """Checks if input is a valid string"""
          if not is_string(inpt):
              return False
          if metadata.get_minimum_string_length() and len(inpt) < metadata.get_minimum_string_length():
              return False
          elif metadata.get_maximum_string_length() and len(inpt) > metadata.get_maximum_string_length():
              return False
          if metadata.get_string_set() and inpt not in metadata.get_string_set():
              return False
          else:
              return True