Added set of set handling (thru concept ISA)

src/core/builtin_concepts.py

@@ -52,6 +52,7 @@ class BuiltinConcepts(Enum):
     NOT_A_SET = "not a set"  # the concept has no entry in sets
     WHERE_CLAUSE_FAILED = "where clause failed"  # failed to validate where clause during evaluation
     CHICKEN_AND_EGG = "chicken and egg"  # infinite recursion when declaring concept
+    ISA = "is a"  # builtin concept to express that a concept is an instance of another one
 
     NODE = "node"
     GENERIC_NODE = "generic node"
@@ -340,8 +341,8 @@ class EnumerationConcept(Concept):
         self.set_metadata_value(ConceptParts.BODY, iteration)
         self.metadata.is_evaluated = True
 
-    def __iter__(self):
-        return iter(self.body)
+    # def __iter__(self):
+    #     return iter(self.body)
 
 
 class ListConcept(Concept):
@@ -353,20 +354,20 @@ class ListConcept(Concept):
     def append(self, obj):
         self.body.append(obj)
 
-    def __len__(self):
-        return len(self.body)
-
-    def __getitem__(self, key):
-        return self.body[key]
-
-    def __setitem__(self, key, value):
-        self.body[key] = value
-
-    def __iter__(self):
-        return iter(self.body)
-
-    def __contains__(self, item):
-        return item in self.body
+    # def __len__(self):
+    #     return len(self.body)
+    #
+    # def __getitem__(self, key):
+    #     return self.body[key]
+    #
+    # def __setitem__(self, key, value):
+    #     self.body[key] = value
+    #
+    # def __iter__(self):
+    #     return iter(self.body)
+    #
+    # def __contains__(self, item):
+    #     return item in self.body
 
 
 class ConceptAlreadyInSet(Concept):