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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 short_string(self):
 """ Compact string representation which doesn't print any of the collection elements. """

        source_str = ""
        if self.sources:
            source_str = " from '%s'" % ",".join(self.sources)
        return "<%s%s with %d elements>" % (
            self.__class__.__name__,
            source_str,
            len(self))