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Frontmatter did not parse to a YAML mapping

Type URI: https://modeled-information-format.github.io/mif-rs/references/errors/frontmatter-not-a-mapping/v1 HTTP status: 422 Exit code: 2 Emitted by: mif-frontmatter (FrontmatterError::NotAMapping)

frontmatter did not parse to a YAML mapping

The frontmatter block parsed as valid YAML, but the top-level value was a bare scalar or sequence, not a mapping (e.g. ---\n- a\n- b\n---). Python’s mif_convert.py reference converter has no equivalent check and would fail later with an unhandled exception instead.

MaybeIncorrect — make the frontmatter block a YAML mapping, not a scalar or sequence.