How to use the apispec.yaml_utils.load_yaml_from_docstring function in apispec

def test_load_yaml_from_docstring_empty_docstring(docstring):
    assert yaml_utils.load_yaml_from_docstring(docstring) == {}

def _operations_from_methods(handler_class):
        """Generator of operations described in handler's http methods

        :param handler_class:
        :type handler_class: RequestHandler descendant
        """
        for httpmethod in yaml_utils.PATH_KEYS:
            method = getattr(handler_class, httpmethod)
            operation_data = yaml_utils.load_yaml_from_docstring(method.__doc__)
            if operation_data:
                operation = {httpmethod: operation_data}
                yield operation

def path_helper(self, operations, view, **kwargs):
        """Path helper that allows passing a Flask view function."""
        rule = self._rule_for_view(view)
        operations.update(yaml_utils.load_operations_from_docstring(view.__doc__))
        if hasattr(view, 'view_class') and issubclass(view.view_class, MethodView):
            for method in view.methods:
                if method in rule.methods:
                    method_name = method.lower()
                    method = getattr(view.view_class, method_name)
                    operations[method_name] = yaml_utils.load_yaml_from_docstring(method.__doc__)
        path = self.flaskpath2openapi(rule.rule)
        app_root = current_app.config['APPLICATION_ROOT'] or '/'
        return urljoin(app_root.rstrip('/') + '/', path.lstrip('/'))

if resource not in resource_uri_mapping:
            raise APISpecError("Could not find endpoint for resource {0}".format(resource))

        operations.update(yaml_utils.load_operations_from_docstring(resource.__doc__) or {})
        path = resource_uri_mapping[resource]["uri"]

        if base_path is not None:
            # make sure base_path accept either with or without leading slash
            # swagger 2 usually come with leading slash but not in openapi 3.x.x
            base_path = '/' + base_path.strip('/')
            path = re.sub(base_path, "", path, 1)

        methods = resource_uri_mapping[resource]["methods"]

        for method_name, method_handler in methods.items():
            docstring_yaml = yaml_utils.load_yaml_from_docstring(method_handler.__doc__)
            operations[method_name] = docstring_yaml or dict()
        return path

if global_meta:
            operations.update(global_meta)
        f_view = getattr(view["callable"], view["attr"])
    # or just function callables
    else:
        f_view = view.get("callable")

    methods = view.get("request_methods")
    view_operations = load_operations_from_docstring(f_view.__doc__)
    if not view_operations:
        view_operations = {}
        if is_string(methods):
            methods = [methods]
        if not methods:
            methods = ALL_METHODS[:]
        operation = load_yaml_from_docstring(f_view.__doc__)
        if operation:
            for method in methods:
                view_operations[method.lower()] = operation
        elif autodoc:
            for method in methods:
                view_operations.setdefault(method.lower(), {"responses": {}})
    operations.update(view_operations)

    return operations