API cleanup: close on commit, isX methods (#145)

## What is the goal of this PR?

As we close transactions on commit at the server end, it makes sense to also close transactions when they are committed at client side. This change does that. Additionally, for user experience reasons, "isX" functions have been added to the Concept interface to determine what variety of Concept an object represents.

## What are the changes implemented in this PR?

We added a try/finally to `commit()` that closes the transaction when it completes or fails.
We added is[Concept] functions to all Concepts indicating if the current Concept is an instance of that Concept variety.

Author: Alex Walker

grakn/concept/concept.py

@@ -23,9 +23,33 @@ class Concept(object):
     def is_type(self):
         return False
 
+    def is_thing_type(self):
+        return False
+
+    def is_entity_type(self):
+        return False
+
+    def is_attribute_type(self):
+        return False
+
+    def is_relation_type(self):
+        return False
+
+    def is_role_type(self):
+        return False
+
     def is_thing(self):
         return False
 
+    def is_entity(self):
+        return False
+
+    def is_attribute(self):
+        return False
+
+    def is_relation(self):
+        return False
+
     def is_remote(self):
         return False
 
@@ -44,5 +68,29 @@ def is_deleted(self):
     def is_type(self):
         return False
 
+    def is_thing_type(self):
+        return False
+
+    def is_entity_type(self):
+        return False
+
+    def is_attribute_type(self):
+        return False
+
+    def is_relation_type(self):
+        return False
+
+    def is_role_type(self):
+        return False
+
     def is_thing(self):
         return False
+
+    def is_entity(self):
+        return False
+
+    def is_attribute(self):
+        return False
+
+    def is_relation(self):
+        return False

grakn/concept/thing/thing.py

@@ -41,15 +41,6 @@ def get_iid(self):
     def is_thing(self):
         return True
 
-    def is_entity(self):
-        return False
-
-    def is_attribute(self):
-        return False
-
-    def is_relation(self):
-        return False
-
     def __str__(self):
         return type(self).__name__ + "[iid:" + self.get_iid() + "]"
 
@@ -142,15 +133,6 @@ def is_deleted(self):
     def is_thing(self):
         return True
 
-    def is_entity(self):
-        return False
-
-    def is_attribute(self):
-        return False
-
-    def is_relation(self):
-        return False
-
     def _thing_stream(self, method: concept_proto.Thing.Req, thing_list_getter: Callable[[concept_proto.Thing.Res], List[concept_proto.Thing]]):
         method.iid = concept_proto_builder.iid(self.get_iid())
         request = transaction_proto.Transaction.Req()

grakn/concept/type/relation_type.py

@@ -75,3 +75,6 @@ def unset_relates(self, role_label: str):
         unset_relates_req.label = role_label
         method.relation_type_unset_relates_req.CopyFrom(unset_relates_req)
         self._execute(method)
+
+    def is_relation_type(self):
+        return True

grakn/concept/type/thing_type.py

@@ -28,6 +28,9 @@ class ThingType(Type):
     def as_remote(self, transaction):
         return RemoteThingType(transaction, self.get_label(), self.is_root())
 
+    def is_thing_type(self):
+        return True
+
 
 class RemoteThingType(RemoteType):
 

grakn/concept/type/type.py

@@ -45,21 +45,6 @@ def is_root(self):
     def is_type(self):
         return True
 
-    def is_thing_type(self):
-        return False
-
-    def is_entity_type(self):
-        return False
-
-    def is_attribute_type(self):
-        return False
-
-    def is_relation_type(self):
-        return False
-
-    def is_role_type(self):
-        return False
-
     def __str__(self):
         return type(self).__name__ + "[label:" + self.get_label() + "]"
 
@@ -110,21 +95,6 @@ def is_abstract(self):
     def is_type(self):
         return True
 
-    def is_thing_type(self):
-        return False
-
-    def is_entity_type(self):
-        return False
-
-    def is_attribute_type(self):
-        return False
-
-    def is_relation_type(self):
-        return False
-
-    def is_role_type(self):
-        return False
-
     def set_supertype(self, _type: Type):
         req = concept_proto.Type.Req()
         supertype_req = concept_proto.Type.SetSupertype.Req()

grakn/rpc/transaction.py

@@ -89,7 +89,10 @@ def commit(self):
         req = transaction_proto.Transaction.Req()
         commit_req = transaction_proto.Transaction.Commit.Req()
         req.commit_req.CopyFrom(commit_req)
-        self._execute(req)
+        try:
+            self._execute(req)
+        finally:
+            self.close()
 
     def rollback(self):
         req = transaction_proto.Transaction.Req()