Put back config property.

tests/test_model.py

@@ -174,6 +174,7 @@ def test_schema(data_model):
             ln.content_type() == ContentType.config)
     assert ca.content_type() == cha.content_type() == ContentType.all
     assert ll.content_type() == ContentType.nonconfig
+    assert lj.config == ca.config == cha.config == (not ll.config) == True
     assert la.ns == ld.ns
     assert lc.ns == "testb"
     assert la.default_value() == 11

yangson/schema.py

@@ -63,6 +63,11 @@ class SchemaNode:
         """Qualified name of the receiver."""
         return (self.name, self.ns)
 
+    @property
+    def config(self) -> bool:
+        """Does the receiver represent configuration?"""
+        return self.content_type().value & ContentType.config.value != 0
+
     def content_type(self) -> ContentType:
         """Receiver's content type."""
         try: