Run a dash app inside a flask app


I currently have a flask app and I want to implement a dash app into it. However I’ve been running into multiple errors and I don’t really understand the document for dash deployment. Here is my code

server = Flask(__name__) 
def dash_chart():

if __name__ == "__main__":

def start():
    app = dash.Dash(__name__)
    app.layout = html.Div('Hello World')
    if __name__=='__main__':