input: 
  import json 
  import sqlite3
  from flask import Flask, request, jsonify 
  
  def fetch_data_from_db():
      """
      Develop an API in Python that fetches data from an SQL database and presents the data in the form of a JSON.
      
      Example:
      For an SQL database with a table 'users' containing columns 'id', 'name', and 'age',
      and having rows (1, 'Alice', 30), (2, 'Bob', 25), the output should be:
      [
          {"id": 1, "name": "Alice", "age": 30},
          {"id": 2, "name": "Bob", "age": 25}
      ]
      """
      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:     
      return app
  