separate pre-processing, add callback parameter to push/pop in python API

src/opt/opt_preprocess.h

@@ -0,0 +1,38 @@
+/*++
+Copyright (c) 2021 Microsoft Corporation
+
+Module Name:
+
+    opt_preprocess.h
+
+Abstract:
+   
+    Pre-processing for MaxSMT
+
+    Find mutexes - at most 1 constraints and modify soft constraints and bounds.
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2022-04-11
+
+--*/
+
+#pragma once
+
+#include "opt/maxsmt.h"
+
+namespace opt {
+
+    class preprocess {
+        ast_manager&     m;
+        solver&          s;
+        expr_ref_vector  m_trail;
+
+        bool find_mutexes(vector<soft>& softs, rational& lower);
+        void process_mutex(expr_ref_vector& mutex, obj_map<expr, rational>& new_soft, rational& lower);
+
+    public:
+        preprocess(solver& s);
+        bool operator()(vector<soft>& soft, rational& lower);
+    };
+};