consistent behavior with other classes

python dictionary operates in-place, so wrappers for out-of-place
behavior let it use like the other DAMASK classes

python/damask/_config.py

@@ -99,6 +99,30 @@ class Config(dict):
             fhandle.write(yaml.dump(self,Dumper=NiceDumper,**kwargs))
 
 
+    def add(self,d):
+        """
+        Add dictionary.
+
+        d : dict
+            Dictionary to append.
+        """
+        duplicate = self.copy()
+        duplicate.update(d)
+        return duplicate
+
+
+    def delete(self,key):
+        """
+        Delete item.
+
+        key : dict
+            Label of the key to remove.
+        """
+        duplicate = self.copy()
+        del duplicate[key]
+        return duplicate
+
+
     @property
     @abc.abstractmethod
     def is_complete(self):

python/tests/test_Config.py

@@ -22,6 +22,10 @@ class TestConfig:
         with open(tmp_path/'config.yaml') as f:
             assert Config.load(f) == config
 
+    def test_add_remove(self):
+        config = Config()
+        assert config.add({'hello':'world'}).delete('hello') == config
+
     def test_repr(self,tmp_path):
         config = Config()
         config['A'] = 1