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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 get_selector(self, name):
 """Find a selector mapped to a style in this or a base style sheet. Args: name (str):
 a style name Returns: :class:`.Selector`: the selector mapped to the style `name` Raises: KeyError: if the style `name` was not found in this or a base style sheet """


        try:
            return self.matcher.by_name[name]
        except (AttributeError, KeyError):
            if self.base is not None:
                return self.base.get_selector(name)
            else:
                raise KeyError("No selector found for style '{}'".format(name))