Need Studio IDML filter to extract translatable text within tag AltText

To apply Accessibility for Ontarians with Disabilities Act(AODA), we have to translate these AltText from the IDML file. Studio's latest filter word 2007-2016 does extract the AltText from docx file. We want the same thing for IDML file.

AltText with the Tag CustomAltText="xxxx" in an IDML file. Let me know if you need any additional information.

Thanks in advance.