in runtool/runtool/datatypes.py [0:0]
def __add__(self, other: Union["Node", "ListNode"]) -> Any:
"""
Returns a new `ListNode` (or any subclass) with `other` appended to `self`.
"""
if isinstance(other, type(self)):
return type(self)(list(self) + list(other))
elif isinstance(other, Node):
return type(self)(list(self) + [other])
raise TypeError