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Description
I'm building a wrapper for this library and a service class for my app and when I wanted to make the formatter exchangeable I realized that I can't typehint the setter against an interface.
https://github.com/geocoder-php/Geocoder/blob/master/src/Common/Formatter/StringFormatter.php
If you agree I'll create a PR and add a Formatter interface that implements the format() method.
Would \Geocoder\Formatter\FormatterInterface.php
work for you?