def concept x is a string pre is_question() as isinstance(x, str)
def concept x is a int pre is_question() as isinstance(x, int)
def concept x is a integer pre is_question() as isinstance(x, int)
def concept x starts with y pre is_question() where x is a string as x.startswith(y)
def concept sha256 from bnf r'[a-f0-9]{64}'
def concept sha512 from bnf r'[a-f0-9]{128}'