'Construct a SequenceMatcher.
Optional arg isjunk is None (the default), or a one-argument
function that takes a sequence element and returns true iff the
element is junk.  None is equivalent to passing "lambda x: 0", i.e.
no elements are considered to be junk.  For example, pass
lambda x: x in " \t"
if you\'re comparing lines as sequences of characters, and don\'t
want to synch up on blanks or hard tabs.
Optional arg a is the first of two sequences to be compared.  By
default, an empty string.  The elements of a must be hashable.  See
also .set_seqs() and .set_seq1().
Optional arg b is the second of two sequences to be compared.  By
default, an empty string.  The elements of b must be hashable. See
also .set_seqs() and .set_seq2().
Optional arg autojunk should be set to False to disable the
"automatic junk heuristic" that treats popular elements as junk
(see module documentation for more information).'

def __init__(self, isjunk=None, a='', b='', autojunk=True):

    self.isjunk = isjunk
    self.a = self.b = None
    self.autojunk = autojunk
    self.set_seqs(a, b)
    return
