def analyse_text(text):
Has to return a float between ``0`` and ``1`` that indicates
if a lexer wants to highlight this text. Used by ``guess_lexer``.
If this method returns ``0`` it won't highlight it in any case, if
it returns ``1`` highlighting with this lexer is guaranteed.

The `LexerMeta` metaclass automatically wraps this function so
that it works like a static method (no ``self`` or ``cls``
parameter) and the return value is automatically converted to
`float`. If the return value is an object that is boolean `False`
it's the same as if the return values was ``0.0``.