>>> import albatross
>>> ctx = albatross.SimpleContext('.')
>>> ctx.locals.a = 20
>>> albatross.Template(ctx, '<magic>', '''
... <al-if expr="a < 15">
...  a (<al-value expr="a">) is less than 15.
... <al-else>
...  a (<al-value expr="a">) is greater than or equal to 15.
... </al-if>
... ''').to_html(ctx)
>>> ctx.flush_content()
a (20) is greater than or equal to 15.