[BUG] Export document // Obsolete and removed function in use

[FailXSiegen]

In all current versions including dev-master, 3.5.x-dev and 3.6.x-dev.

The issue:
If you are using the data director to export documents from objects an error occurs.

The lib/Pim/Item/Importer.php has an issue with removed functions since pimcore v 11
getContentMasterDocument() and setContentMasterDocument()
which are replaced with getContentMainDocument() and setContentMainDocument().

A simple str_replace from the functions did not help due to changes in the required set parameter object from the setContentMainDocument() function.

Type error Expected type 'Pimcore\Model\Element\ElementInterface'. Found 'Pimcore\Model\AbstractModel'.