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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 concept(self, cid, **kwargs):
        ''' Get concept by concept ID '''
        if cid not in self.__concept_map:
            if 'default' in kwargs:
                return kwargs['default']
            else:
                raise KeyError("Invalid cid")
        else:
            return self.__concept_map[cid]