An event handler applies to a specific start element event within the XML event stream (except for default handlers).

          !Matcher
        

Example:

    contexts:
      - !Context
        name: headline
        defaultHandler:
          !Handler
          eventMatcher: !Matcher { qname: *p, classes: *headline_styles }
          ...

    # alternative (equivalent) YAML style
    contexts:
      - !Context
        name: headline
        defaultHandler:
          !Handler
          eventMatcher:
            !Matcher
            qname: *p
            classes: *headline_styles
            ...