sample_listCards: fix PEP8 warnings
sample_listCards: fix PEP8 warnings

sample_listCards.py:40:51: E502 the backslash is redundant between brackets
sample_listCards.py:48:79: E502 the backslash is redundant between brackets
sample_listCards.py:55:49: E502 the backslash is redundant between brackets
sample_listCards.py:73:53: E502 the backslash is redundant between brackets
sample_listCards.py:84:1: E402 module level import not at top of file

LudovicRousseau/pyscard,LudovicRousseau/pyscard,LudovicRousseau/pyscard