add section on documentation and duck typing.

docs/source/_get-started/making_connections.rst

@@ -1,6 +1,9 @@
 Connecting Nodes
 ================
 
+Building a Connection
+---------------------
+
 ..
  **# TODO: Connect function and class based nodes**
 
@@ -41,4 +44,40 @@ With this, any attribute of any Node can be connected.
 
  with zntrack.DiGraph() as graph:
  generate_data = GenerateData(**kwargs)
- process_data = ProcessData(data=generate_data.data)
+ process_data = ProcessData(data=generate_data.data)
+
+Write documentation
+-------------------
+ZnTrack Nodes are designed to be flexible and easy to connect.
+This is achieved through the concept of `duck typing <https://en.wikipedia.org/wiki/Duck_typing>`_, which allows Nodes to be connected as long as they have the correct attributes and methods.
+To help document the required attributes and methods, we suggest using the ``typing.Protocol`` module.
+
+For example, consider the Node ``ProcessData``, which expects an attribute ``data`` of type ``np.ndarray``.
+We can define such a ``typing.Protocol`` as follows:
+
+.. code-block:: python
+
+ import typing
+ import numpy as np
+
+ class HasData(typing.Protocol):
+ """Protocol for Nodes with data attribute"""
+ data: np.ndarray
+
+Then, we can use this ``HasData` protocol as a type hint for the ``input_data`` attribute of the ``ProcessData`` Node:
+
+.. code-block:: python
+
+ from zntrack import Node, zn
+
+ class ProcessData(Node):
+ input_data: HasData | list[HasData] = zn.deps()
+
+ def run(self):
+ if not isinstance(self.input_data, list):
+ self.input_data = [self.input_data]
+
+ for data_node in self.input_data:
+ print(data_node.data.shape)
+
+This highlights, that the ``ProcessData`` Node should work with any Node that has a ``data`` attribute of type ``np.ndarray``, whether it is a NumPy array generated by another Node from the same package, or generated by a Node from an entirely different library.