How to combine 2 plots stored in BytesIO in one file to attach in webex teams message

Hello All…I really stuck this last step. I got a code that will plot 2 charts and send attachment on webex teams. I followed the sample code below.
But I got error:

TypeError: expected string or bytes-like object, got 'tuple'

The sample code is below:

import pandas as pd
import matplotlib.pyplot as plt
from io import BytesIO
from webexteamssdk import WebexTeamsAPI

# Assuming you have a DataFrame named df

def generate_plot1(df):
    plt.figure(figsize=(8, 6))
    plt.plot(df['x'], df['y'])
    plt.title('Plot 1')
    plot1_buf = BytesIO()  
    plt.savefig(plot1_buf, format='png')  
    return plot1_buf

def generate_plot2(df):
    plt.figure(figsize=(8, 6))
    plt.scatter(df['x'], df['y'])
    plt.title('Plot 2')
    plot2_buf = BytesIO()  
    plt.savefig(plot2_buf, format='png')  
    return plot2_buf

def send_webex_message(api, room_id_or_email, text, files):
    message = {
        'roomId': room_id_or_email,
        'text': text,
        'files': files

# Initialize the API with your access token
api = WebexTeamsAPI(access_token='YOUR_ACCESS_TOKEN')

# Define the room ID or email address where you want to send the images
room_id_or_email = 'ROOM_ID_OR_EMAIL'

# Generate plots
plot1_buf = generate_plot1(df)
plot2_buf = generate_plot2(df)

# Convert BytesIO buffers to streams
plot1_stream =
plot2_stream =

# Prepare message files
files = [
    ('plot1.png', plot1_stream, 'image/png'),
    ('plot2.png', plot2_stream, 'image/png')

# Send the message
send_webex_message(api, room_id_or_email, 'Here are the plots!', files)

Any helps would be appreciated!

Sample result is below image…thanks