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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def iter_filths():
 """Iterate over all instances of filth"""

    for filth_cls in iter_filth_clss():
        if issubclass(filth_cls, RegexFilth):
            m = next(re.finditer(r"\s+", "fake pattern string"))
            yield filth_cls(m)
        else:
            yield filth_cls()