Reorganize callbacks

tests/solvers/test_lazy_cb.py

@@ -1,27 +0,0 @@
-#  MIPLearn: Extensible Framework for Learning-Enhanced Mixed-Integer Optimization
-#  Copyright (C) 2020-2021, UChicago Argonne, LLC. All rights reserved.
-#  Released under the modified BSD license. See COPYING.md for more details.
-
-import logging
-from typing import Any
-
-from miplearn.solvers.gurobi import GurobiSolver
-from miplearn.solvers.internal import InternalSolver
-
-logger = logging.getLogger(__name__)
-
-
-def test_lazy_cb() -> None:
-    solver = GurobiSolver()
-    instance = solver.build_test_instance_knapsack()
-    model = instance.to_model()
-
-    def lazy_cb(cb_solver: InternalSolver, cb_model: Any) -> None:
-        cobj = (cb_model.getVarByName("x[0]") * 1.0, "<", 0.0, "cut")
-        if not cb_solver.is_constraint_satisfied(cobj):
-            cb_solver.add_constraint(cobj)
-
-    solver.set_instance(instance, model)
-    solver.solve(lazy_cb=lazy_cb)
-    solution = solver.get_solution()
-    assert solution["x[0]"] == 0.0