input: 
  def fetch_sql_data_to_json() -> str:
      """ Fetches data from an SQL database and presents the data in the form of a JSON using a Flask API.
      The API endpoint returns a JSON representation of all users in the database.
      >>> fetch_sql_data_to_json().startswith('[{"id":')
      True
      >>> fetch_sql_data_to_json().endswith('}]')
      True
      """
      import json
      import sqlite3
      from flask import Flask, request, jsonify
  
      app = Flask(__name__)
  
      def dict_factory(cursor, row):
          d = {}
          for idx, col in enumerate(cursor.description):
              d[col[0]] = row[idx]
          return d
  
      @app.route('/', methods=['GET'])
      def index():
          connection = sqlite3.connect('database.db')
          connection.row_factory = dict_factory
          cur = connection.cursor()
          all_users = cur.execute('SELECT * FROM users;').fetchall()
          return jsonify(all_users)
  
      if __name__ == '__main__':
          app.run(debug=True)
  
output:     with app.test_client() as client:
          response = client.get('/')
          return response.get_data(as_text=True)