docs: def parse_model_group(path, group):
      """Parse a structured model group as obtained from a YAML file
  
      Path can be given as a string or a context.
      """
  
      context = FilePathContext(path)
  
      for reaction_id in group.get('reactions', []):
          yield reaction_id
  
      # Parse subgroups
      for reaction_id in parse_model_group_list(
              context, group.get('groups', [])):
          yield reaction_id