convert boolean to int to satisfy solver requirements

app/helpers/common_helper.py

@@ -0,0 +1,5 @@
+def boolean_to_int(value: bool) -> int:
+    if value:
+        return 1
+    else:
+        return 0

app/helpers/solver_helper.py

@@ -3,6 +3,8 @@ from random import randint, sample
 
 import logging
 
+from helpers.common_helper import *
+
 from models.bundle import Bundle
 from models.solver_run import SolverRun
 from models.item import Item
@@ -26,7 +28,7 @@ def build_constraints(solver_run: SolverRun, problem: LpProblem,
                 logging.info('Metadata Constraint Generating...')
                 con = dict(
                     zip([item.id for item in solver_run.items], [
-                        item.attribute_exists(attribute)
+                        boolean_to_int(item.attribute_exists(attribute))
                         for item in solver_run.items
                     ]))
                 problem += lpSum(