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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 set_functions(self, functions):
 """Check functions passed as argument and set them to be used."""

        for func in functions:
            try:
                self.append_function(func)
            except (ValueError, AttributeError) as ex:
                log.error("'%s' is not a callable function: %s", func, ex)
                raise