This is the documentation for the unsupported version 2.2. Please consider upgrading your code to the latest stable version
Upgrading from 2.1 to 2.2
Deprecation of MarkdownConverterInterface
The MarkdownConverterInterface and its convertToHtml() method were deprecated in 2.2.0 and will be removed in 3.0.0.
You should switch your implementations to use ConverterInterface and convert() instead which provide the same behavior.