Adds encode to the Context class and tests encode / decode

Signed-off-by: ncordon <nacho.cordon.castillo@gmail.com>

Author: ncordon

bblfsh/context.py

@@ -15,5 +15,9 @@ def iterate(self, order: int) -> iterator:
         TreeOrder.check_order(order)
         return iterator(self.root, order)
 
+    def encode(self, fmt: int):
+        encoded = self.ctx.encode(self.root, fmt)
+        return encoded
+
 def context(root: dict) -> Context:
     return Context(root)

bblfsh/test.py

@@ -560,6 +560,16 @@ def testPythonContextFilter(self) -> None:
         for nodeC, nodePy in zip(itC, itPy):
             self.assertEqual(nodeC.get(), nodePy)
 
+    def testEncodeDecodePythonContext(self) -> None:
+        # C++ memory context
+        ctxC = self._parse_fixture()
+        # Python memory context
+        pyDict = ctxC.root.get()
+        ctxPy = bblfsh.context(pyDict)
+        encoded = ctxPy.encode(fmt = 1) # YAML
+        decoded = decode(encoded, format = 1)
+
+        self.assertEqual(encoded, decoded.load())
 
 if __name__ == "__main__":
     unittest.main()