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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_category(self, category: str = None) -> 'PygalleBaseClass': """ Define the category of the class. # Arguments category: The name of category. # Returns: PygalleBaseClass: An instance of :class:`PygalleBaseClass` """

        return self.set_internal(PygalleBaseClass.__KEYS.CATEGORY, category)