Create Custom Header for Article Page - C#

  using (var ctx = new OfficeDevPnP.Core.AuthenticationManager().GetAppOnlyAuthenticatedContext(newSiteUrl, clientId, clientSecret))
            {
                var pages = ctx.Web.Lists.GetByTitle("Site Pages");
                ctx.Load(pages);
                
                //get template page
                var templatePage = pages.RootFolder.GetFile("Project-Home.aspx").ListItemAllFields;
                ctx.Load(templatePage);
                ctx.ExecuteQuery();
                
                //this is our template page content
                var _customPageHeader = templatePage[ClientSidePage.PageLayoutContentField]; //LayoutWebpartsContent
                var _canvasContent = templatePage["CanvasContent1"];

                //create new page in site page library
                var item = pages.RootFolder.Files.AddTemplateFile("/sites/test/sitepages/BeauTest.aspx", TemplateFileType.ClientSidePage).ListItemAllFields;
              
               //update page header from template information
                item[ClientSidePage.PageLayoutContentField] = _customPageHeader;        
                item[ClientSidePage.ClientSideApplicationId] = ClientSidePage.SitePagesFeatureId; //ClientSideApplicationId - b6917cb1-93a0-4b97-a84d-7cf49975d4ec
                item["CanvasContent1"] = _canvasContent; //"<div></div>";
                item["_TopicHeader"] = "Service Line";
                
                item.Update();
                ctx.Load(item);
                ctx.ExecuteQuery();
            }