docs: def _dump_spec(spec):
      """Dump bel specification dictionary using YAML
  
      Formats this with an extra indentation for lists to make it easier to
      use cold folding on the YAML version of the spec dictionary.
      """
      with open("spec.yaml", "w") as f:
          yaml.dump(spec, f, Dumper=MyDumper, default_flow_style=False)