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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 add_limbs(self, key=None):
        ''' Add a new section from the tree into the existing os environment

        Parameters:
            key (str):
                The section name to grab from the environment

        '''
        self.branch_out(limb=key)
        self.add_paths_to_os(key=key)