def __init__(self, clslist):
if not hasattr(clslist, '<STR_LIT>'):<EOL><INDENT>clslist = [clslist]<EOL><DEDENT>self.required = reduce(set.union, (cls.required for cls in clslist if issubclass(cls, AttributeMapper)))<EOL>self.optional = reduce(set.union, (cls.optional for cls in clslist if issubclass(cls, AttributeMapper)))<EOL>self.optional.symmetric_difference_update(self.required)<EOL>
SCFilter(clslist)

Args:
    clslist (list): List of classes from which to build the filter

Returns:
    new SCFilter instance