Why is missing-text set?

[sanmai-NL]

At

docling-core/docling_core/types/doc/document.py

Line 2140 in f464be5

text = "<missing-text>"

this value is set.

This value pops up as DoclingDocument's export_to_markdown() return value in some cases. What's the benefit of this placeholder over the empty string? Using the empty string allows us to detect missing text in a standard (Pythonic) way, using truthiness or length.