I don't really know how I stumbled upon this, and I don't know what to think about it, but apparently
 = 
 = ''
'' = 
This is related to Python's multiple assignment (sequence unpacking):
a, b, c = 1, 2, 3
works the same as:
[a, b, c] = 1, 2, 3
What you've discovered is the degenerative case: empty sequences on both sides. Syntactically valid because it's a list rather than a tuple. Nice find; never thought to try that before!