Updated sheerka.value() and added unit tests

core/sheerka.py

@@ -546,7 +546,7 @@ class Sheerka(Concept):
             return from_db
 
         # else return new Unknown concept
-        # Note that I don't call the new() method, as it use get() -> cyclic call
+        # Note that I don't call the new() method to prevent cyclic call
         unknown_concept = Concept()
         template = self.concepts_cache[str(BuiltinConcepts.UNKNOWN_CONCEPT)]
         unknown_concept.update_from(template)
@@ -623,7 +623,7 @@ class Sheerka(Concept):
         if self.isinstance(obj, BuiltinConcepts.RETURN_VALUE) and \
             obj.status and \
             self.isinstance(obj.value, BuiltinConcepts.USER_INPUT):
-            return obj.value.text
+            return obj.value.body
 
         if not isinstance(obj, Concept):
             return obj
@@ -632,7 +632,10 @@ class Sheerka(Concept):
             return obj.get_value()
 
         if obj.body is not None:
-            return obj.body
+            if (isinstance(obj.body, list) or isinstance(obj.body, set)) and len(obj.body) == 1:
+                return obj.body[0]
+            else:
+                return obj.body
 
         return obj if allow_none_body else self.new(BuiltinConcepts.CANNOT_RESOLVE_VALUE_ERROR, body=obj)