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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 _next(self, possible_solution):
 """Where the magic happens. Produces a generator that returns all solutions given a base solution to start searching. """

        # bail out if we have seen it already. See __iter__ to where seen is initially set.
        # A complete solution has all its variables set to a particular value.
        is_complete = (len(possible_solution) == len(self._vars))

        if is_complete:
            self._solutions_seen += 1
            if self.satisfies_constraints(possible_solution):
                yield dict(possible_solution)
        else:
            if self.is_feasible(possible_solution):
                for s in self.derived_solutions(possible_solution):
                    for solution in self._next(s):
                        yield solution