Fixed error when desc() returns multiple results

src/core/sheerka/Sheerka.py

@@ -916,6 +916,19 @@ class Sheerka(Concept):
 
         return a.key == b_key
 
+    @staticmethod
+    def isin(a, b):
+        """
+        True if the concept is the list
+        :param a:
+        :param b:
+        :return:
+        """
+        if not isinstance(a, Concept):
+            return False
+
+        return a.key in b
+
     @staticmethod
     def get_unknown(metadata):
         """