def METHOD_NAME(self, text):
    """Remove prefix from text for command processing.
    Returns:
        prefix: One of PREFIXES.
        command: Rest of the text stripped from whitespace.
    """
    prefix, command = text[0], text[1:]
    if prefix not in self.PREFIXES:
        possible = utils.quotedjoin(self.PREFIXES)
        raise ValueError(f"Unknown prefix '{prefix}', possible values: {possible}")
    command = command.strip()
    return prefix, command