pression
    does *not* match at the current position.  Also, ``NotAny`` does
    *not* skip over leading whitespace. ``NotAny`` always returns
    a null token list.  May be constructed using the ``'~'`` operator.

    Example::

        AND, OR, NOT = map(CaselessKeyword, "AND OR NOT".split())

        # take care not to mistake keywords for identifiers
        ident = ~(AND | OR | NOT) + Word(alphas)
        boolean_term = Opt(NOT) + ident

        # very crude boolean expression - to support parenthesis groups and
        # operation hierarchy, use infix_notation
        boolean_expr = boolean_term + ((AND | OR) + boolean_term)[...]

        # integers that are followed by "." are actually floats
        integer = Word(nums) + ~Char(".")
    rą