PlantUML is a component that allows you to quickly write:

• Sequence diagram

  @startuml
  Alice -> Bob: Authentication Request
  Bob --> Alice: Authentication Response
  Alice -> Bob: Another authentication Request
  Alice <-- Bob: Another authentication Response
  @enduml

  

• Usecase diagram

• Class diagram

• Object diagram

• Activity diagram (here is the legacy syntax)

• Component diagram

• Deployment diagram

• State diagram

• Timing diagram

GitHub - plantuml/plantuml: Generate diagrams from textual description
Official Javadoc Documentation: Overview (plantuml 1.2024.7beta2 API)

If you need to convert files from one markup format into another, pandoc is your swiss-army knife. Pandoc can convert documents in markdown, reStructuredText, textile, HTML, DocBook, LaTeX, MediaWiki markup, TWiki markup, OPML, Emacs Org-Mode, Txt2Tags, Microsoft Word docx, EPUB, or Haddock markup to

HTML formats: XHTML, HTML5, and HTML slide shows using Slidy, reveal.js, Slideous, S5, or DZSlides.
Word processor formats: Microsoft Word docx, OpenOffice/LibreOffice ODT, OpenDocument XML
Ebooks: EPUB version 2 or 3, FictionBook2
Documentation formats: DocBook, GNU TexInfo, Groff man pages, Haddock markup
Page layout formats: InDesign ICML
Outline formats: OPML
TeX formats: LaTeX, ConTeXt, LaTeX Beamer slides
PDF via LaTeX
Lightweight markup formats: Markdown, reStructuredText, AsciiDoc, MediaWiki markup, DokuWiki markup, Emacs Org-Mode, Textile
Custom formats: custom writers can be written in lua.

UnicodeDecodeError: ‘ascii’ codec can’t decode byte 0xd1 in position 1: ordinal not in range(128) (Why is this so hard??)
One of the toughest things to get right in a Python program is Unicode handling. If you’re reading this, you’re probably in the middle of discovering this the hard way.

The main reasons Unicode handling is difficult in Python is because the existing terminology is confusing, and because many cases which could be problematic are handled transparently. This prevents many people from ever having to learn what’s really going on, until suddenly they run into a brick wall when they want to handle data that contains characters outside the ASCII character set.

AsciiDoc is a lightweight markup language for authoring notes, articles, documentation, books, web pages, slide decks and man pages in plain text. This guide is a quick reference for the common AsciiDoc document and text formatting markup

If you need to convert files from one markup format into another, pandoc is your swiss-army knife. Pandoc can convert documents in markdown, reStructuredText, textile, HTML, DocBook, LaTeX, MediaWiki markup, TWiki markup, OPML, Emacs Org-Mode, Txt2Tags, Microsoft Word docx, EPUB, or Haddock markup to

HTML formats: XHTML, HTML5, and HTML slide shows using Slidy, reveal.js, Slideous, S5, or DZSlides.
Word processor formats: Microsoft Word docx, OpenOffice/LibreOffice ODT, OpenDocument XML
Ebooks: EPUB version 2 or 3, FictionBook2
Documentation formats: DocBook, GNU TexInfo, Groff man pages, Haddock markup
Page layout formats: InDesign ICML
Outline formats: OPML
TeX formats: LaTeX, ConTeXt, LaTeX Beamer slides
PDF via LaTeX
Lightweight markup formats: Markdown, reStructuredText, AsciiDoc, MediaWiki markup, DokuWiki markup, Emacs Org-Mode, Textile
Custom formats: custom writers can be written in lua.