Sorry, I didn't mean to mislead. I wrote "easily" - I guess using the current textwrap.dedent isn't really hard, but still, writing:
import textwrap ....
r = some_func(textwrap.dedent('''\ line1 line2'''))
Seems harder to me than simply
r = some_func('''\ line1 line2'''.dedent())
This example brings up another reason why "dedent" us a method is a good idea: It is a common convention to indent things according to the last opening bracket. "dedent" as a function makes the indentation grow in at least 7 characters, and in 16 characters if you don't do "from textwrap import dedent".
It's a common convention, but a rather ugly one. It makes harder breaking lines at 78-80 chars, and using long enough identifiers.
I find it more useful to go straight to the next line, indenting the usual four spaces (and also separating nested stuff):
r = some_func( textwrap.dedent( '''\ line1 line2'''))
This style uses up more vertical space, but I find it also gives code a clearer overall shape.