input: Write a function to create a Flask application that submits form data containing Name, Email, and Phone and stores it in an SQLite database. The function should return the Flask application object.
  
  assert create_flask_app() is not None
  assert create_flask_app().name == 'Flask'
  assert hasattr(create_flask_app(), '__name__') == True
  assert callable(create_flask_app().run) == True
output: 
  def create_flask_app():
      from flask import Flask, request, render_template_string
      import sqlite3
  
      app = Flask(__name__)
  
      conn = sqlite3.connect('form_data.db')
      c = conn.cursor()
      c.execute('''CREATE TABLE IF NOT EXISTS form_data
                   (name TEXT, email TEXT, phone TEXT)''')
      conn.commit()
      conn.close()
  
      @app.route('/', methods=['GET', 'POST'])
      def index():
          if request.method == 'POST':
              name = request.form['name']
              email = request.form['email']
              phone = request.form['phone']
  
              conn = sqlite3.connect('form_data.db')
              c = conn.cursor()
              c.execute("INSERT INTO form_data (name, email, phone) VALUES (?, ?, ?)", (name, email, phone))
              conn.commit()
              conn.close()
  
              return "Data submitted successfully!"
  
          return render_template_string('''
              <form method="post">
                  Name: <input type="text" name="name"><br>
                  Email: <input type="text" name="email"><br>
                  Phone: <input type="text" name="phone"><br>
                  <input type="submit" value="Submit">
              </form>
          ''')
  
      return app
  