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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 is_private(self, key, sources):
 """Check if attribute is private."""

        # aliases are always public.
        if key == ENTRY.ALIAS:
            return False
        return all([
            SOURCE.PRIVATE in self.get_source_by_alias(x)
            for x in sources.split(',')
        ])