docs: def build_metadata_class(specfile):
      """Generate a metadata class for the specified specfile."""
      with open(specfile) as f:
          spec = json.load(f)
          name = os.path.basename(specfile).split('.')[0]
          spec['name'] = name
  
          env = get_jinja_env()
  
          metadata_template = env.get_template('metadata.py.jinja2')
          with open('pycanvas/meta/{}.py'.format(name), 'w') as t:
              t.write(metadata_template.render(spec=spec))