def _add_implicit_connections(self, connections):
        """
        Finds all matches between promoted names of parameters and unknowns
        in this `Problem`.  Any matches imply an implicit connection.
        All connections are expressed using absolute pathnames and are
        added to the dict of explicit connections passed in.

        Args
        ----
        connections : dict
            A dict containing all explicit connections.

        Returns
        -------
        set
            promoted parameters in this `Problem` that are not implicitly
            connected

        """

        dangling = set()

        abs_unames = self.root._sysdata.to_abs_uname

        for prom_name, pabs_list in iteritems(self.root._sysdata.to_abs_pnames):
            if prom_name in abs_unames:  # param has a src in unknowns
                for pabs in pabs_list:
                    connections.setdefault(pabs, []).append((abs_unames[prom_name], None))
            else:
                dangling.add(prom_name)

        return dangling
dataset/ETHPy150Open OpenMDAO/OpenMDAO/openmdao/core/problem.py/Problem._add_implicit_connections/original