我想创建一个用户可以上传CSV文件的应用程序，它将显示一个数据表，用户可以编辑，添加列和添加行。还有两个下拉列表，其中包含数据表的列的值。但是我在运行代码后加载依赖项时出错。谁能教我如何解决此错误？

下面是代码：

import base64
import io
import dash
from dash.dependencies import Input,Output,State
import dash_core_components as dcc
import dash_html_components as html
import dash_table
import pandas as pd
from dash.exceptions import PreventUpdate

external_stylesheets = ['https://codepen.io/chriddyp/pen/bWLwgP.css']

app = dash.Dash(__name__,external_stylesheets=external_stylesheets)
app.config.suppress_callback_exceptions = True
app.layout = html.Div([
    dcc.Upload(
        id='datatable-upload',children=html.Div([
            'Drag and Drop or ',html.A('Select Files')
        ]),style={
            'width': '100%','height': '60px','lineHeight': '60px','borderWidth': '1px','borderStyle': 'dashed','borderRadius': '5px','textAlign': 'center','margin': '10px'
        },),html.Div([
        dcc.Input(
            id='adding-rows-name',placeholder='Enter a column name...',value='',style={'padding': 10}
        ),html.Button('Add Column',id='adding-rows-button',n_clicks=0)
    ],style={'height': 50}),html.Div(id='output-data-upload'),html.Button('Add Row',id='editing-rows-button',n_clicks=0),dcc.Dropdown(
        id='data_selector1',options=[       
            {'label': '','value': ''}
        ],value=[]
    ),dcc.Dropdown(
        id='data_selector2',])


def parse_contents(contents,filename):
    content_type,content_string = contents.split(',')
    decoded = base64.b64decode(content_string)
    if 'csv' in filename:
        # Assume that the user uploaded a CSV file
        return pd.read_csv(
            io.StringIO(decoded.decode('utf-8')))
    elif 'xls' in filename:
        # Assume that the user uploaded an excel file
        return pd.read_excel(io.BytesIO(decoded))


@app.callback(Output('output-data-upload','children'),[Input('datatable-upload','contents')],[State('datatable-upload','filename')])
def update_output(contents,filename):
    if contents is None:
        return []
    df = parse_contents(contents,filename)
    return html.Div([
        dash_table.DataTable(
            id='table',style_data={
                     'whiteSpace': 'normal','height': 'auto'
                     },style_table={'overflowX': 'scroll','maxHeight': '300','overflowY': 'scroll'},style_cell={                     
                     'minWidth': '150px','maxWidth': '180px','whiteSpace': 'normal','textAlign': 'left'
                },style_header={                   
                    'fontWeight': 'bold',},fixed_rows={ 'headers': True,'data': 0 },columns=[{"name": i,"id": i,'deletable': True,'renamable': True} for i in df.columns],data=df.to_dict("records"),row_deletable=True,filter_action="native",sort_action="native",sort_mode='multi',editable=True,)
    ])

#The code will work if I remove this function     
@app.callback(                   
    Output('table','data'),[Input('editing-rows-button','n_clicks')],[State('table',State('table','columns')])
def add_row(n_clicks,rows,columns):
    if n_clicks > 0:
        rows.append({i['id']: '' for i in columns})
    return rows

@app.callback(
    Output('table','columns'),[Input('adding-rows-button',[State('adding-rows-name','value'),'columns')])
def update_columns(n_clicks,value,existing_columns):
    if n_clicks > 0:
        existing_columns.append({
            'id': value,'name': value,'renamable': True,'deletable': True
        })
    return existing_columns

@app.callback(Output('data_selector1','options'),[Input('table','data')])
def update_dropdown(rows):
    if rows is None:
        raise PreventUpdate
    df = pd.DataFrame(rows)
    print('updating menus')
    columns = df.columns
    col_labels = [{'label': k,'value': k} for k in columns]
    return col_labels

@app.callback(Output('data_selector2','data')])
def update_dropdown2(rows):
    if rows is None:
        raise PreventUpdate
    df = pd.DataFrame(rows)
    print('updating menus')
    columns = df.columns
    col_labels = [{'label': k,'value': k} for k in columns]
    return col_labels


if __name__ == '__main__':
    app.run_server(debug=False)

如果我删除数据表函数中的添加行，则代码将起作用。