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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 _checkout(self, treeish):
        '''
        Helper function to checkout something

        :param treeish:
            String for '`tag`', '`branch`', or remote tracking '-B `banch`'
        '''

        return self.m(
            'checking out "%s"' % (treeish),
            cmdd=dict(cmd='git checkout %s' % (treeish), cwd=self.local),
            verbose=False
        )