docs: def is_separator(self, char):
          """
          Test if a character is a separator.
  
          Parameters
          ----------
          char : str
              The character to test.
  
          Returns
          -------
          ret : bool
              True if character is a separator, False otherwise.
  
          """
          if len(char) > 1:
              raise TypeError("Expected a char.")
          if char in self.separators:
              return True
          return False