Fixed two small bugs, one involving use of is for string comparison, the other...

Fixed two small bugs, one involving use of is for string comparison, the other involving an incorrect function call when a restraint is added to the system with only one argument

mrdna/arbdmodel/__init__.py

@@ -311,7 +311,7 @@ class Child():
 
         """
         # if self.parent is not None:
-        if "parent" not in self.__dict__ or self.__dict__["parent"] is None or name is "children":
+        if "parent" not in self.__dict__ or self.__dict__["parent"] is None or name == "children":
             raise AttributeError("'{}' object has no attribute '{}'".format(type(self).__name__, name))
 
 
@@ -1215,7 +1215,7 @@ component "data" value 3
                 item = [i.idx]
                 if len(restraint) == 1:
                     item.append(restraint[0])
-                    item.extend(i.get_collapsed_position())
+                    item.extend(i.collapsedPosition())
                 elif len(restraint) == 2:
                     item.append(restraint[0])
                     item.extend(restraint[1])