graph-depends: fix code style

Fix these warnings:
E122 continuation line missing indentation or outdented
E127 continuation line over-indented for visual indent
E128 continuation line under-indented for visual indent
E202 whitespace before ']'
E221 multiple spaces before operator
E225 missing whitespace around operator
E231 missing whitespace after ','
E302 expected 2 blank lines, found 1
E305 expected 2 blank lines after class or function definition, found 1
E502 the backslash is redundant between brackets
E713 test for membership should be 'not in'

Signed-off-by: Ricardo Martincoski <ricardo.martincoski@gmail.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>