Added docs section on Python typing

docs/python_typing.md

@@ -0,0 +1,38 @@
+## Introduction to Python type hints
+
+### Duck typing in Python
+
+The concept of "duck-typing" is a central concept in Python. The name comes from the 
+[Duck test](https://en.wikipedia.org/wiki/Duck_test):
+
+"If it looks like a duck, swims like a duck, and quacks like a duck, then it probably _is_ a duck"
+
+This again is a reference to the 
+["Canard Digérateur"](https://en.wikipedia.org/wiki/Digesting_Duck), or "The Digesting Duck", a 
+mechanical duck built by [Jacques de Vaucanson](https://en.wikipedia.org/wiki/Jacques_de_Vaucanson) 
+in 1739:
+
+![The Digesting Duck](https://en.wikipedia.org/wiki/Duck_test#/media/File:Vaucanson_duck2.gif)
+
+The duck was designed to look like it ate a mixture of water and grain, digested the food, and then 
+excreted the remains. In reality, the duck excreted a pre-made mixture of bread crumbs and green dye 
+in a process that was not connected to the ingestion process.
+
+Similarly, in Python, the type of an object is determined dynamically - by its behavior - rather 
+than by definition. This is in contrast to statically typed languages like C++ or Java, where the
+type of an object is specified at compile time. In Python, the type of an object is determined at
+runtime, allowing a level of dynamics not easily achieved in statically typed languages, e.g.:
+
+```python
+def add(x, y):
+    return x + y
+
+a = add(1, 2)  # type(a) == int; a == 3
+b = add('foo', 'bar')  # type(b) == str; b == 'foobar'
+c = add([1, 2], [3, 4])  # type(c) == list; c == [1, 2, 3, 4]
+```
+
+In the above example, the `add` function is defined to take two arguments and return their sum, 
+regardless of the type of the arguments. The types output by the function are determined at runtime
+based on the input types. This is an example of 
+[duck-typing](https://en.wikipedia.org/wiki/Duck_typing) in Python.

mkdocs.yml

@@ -35,6 +35,7 @@ nav:
 - Omnipy: index.md
 - Install: install.md
 - Getting started: getting_started.md
+- Intro to Python typing: python_typing.md
 - Contributing: contributing.md
 - Release notes: release_notes.md
 - Code Reference: reference/