PythonAnywhereでFlaskアプリケーションが 'ModuleNotFoundError: No module named flask_mysqldb' エラーを起こす

from flask import Flask, render_template, request, redirect
from flask_mysqldb import MySQL
from config import Config

app = Flask(__name__)
app.config.from_object(Config)
mysql = MySQL(app)

@app.route('/', methods=['GET', 'POST'])
def index():
    if request.method == 'POST':
        content = request.form['content']
        cur = mysql.connection.cursor()
        cur.execute("INSERT INTO posts (content) VALUES (%s)", (content,))
        mysql.connection.commit()
        cur.close()
        return redirect('/')
    
    cur = mysql.connection.cursor()
    cur.execute("SELECT * FROM posts ORDER BY created_at DESC")
    posts = cur.fetchall()
    cur.close()
    return render_template('index.html', posts=posts)

if __name__ == '__main__':
    app.run(debug=True)