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Biryani Design
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Features
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* Procedural, not declarative: Every converter is a function.

* Bad input isn’t exceptional: Converters don't raise exceptions they return a couple (value, error).

* No value is not a value: When a converter is called with ``None`` it does nothing since it has no value to convert and returns ``(None, None)``.

* No magic: No decorator, no metaclass, no class, ..., nothing but simple functions.

* Once again: No class. No attribute to define, no method to override, no instance to create.

* No symmetry: A conversion from A to B is not handled by the same converter as a conversion from B to A.

* Lean and mean: Each converter does only one thing. To do more, combine converters.

* Easy combination: Every converter can be combined with any other converters.

* Homogeneity: Every converter has the same signature (input: the value and an optional context, output: a couple (converted value, error)).

* Extensibility: Creating a converter means just writing a new function with the same signature.


Consequences
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* Using a converter is just calling a function.

* Creating a new converter is easy.

* But combining existing converters is even easier.

* Mixing converters with Python code is as easy.

* Converters enhancements are incremental.

* *Biryani* can be used to validate and/or convert anything to anything (HTML forms, CSV files, XML files, etc).