#NEWLINE# def __init__( self , content = None ) : #NEWLINE# #INDENT# "\n        Initializer.\n\n        The argument is either a pattern or None.  If it is None, this\n        only matches an empty sequence (effectively '$' in regex\n        lingo).  If it is not None, this matches whenever the argument\n        pattern doesn't have any matches.\n        " #NEWLINE# if ( content is not None ) : #NEWLINE# #INDENT# assert isinstance ( content , BasePattern ) , repr ( content ) #NEWLINE# #UNINDENT# self . content = content