input: def fetch_data_from_sql():
      """Develop an API in Python that fetches data from an SQL database and presents the data in the form of a JSON.
      >>> data = fetch_data_from_sql()
      >>> isinstance(data, dict)
      True
      """
output:     import sqlite3
      import json
  
      conn = sqlite3.connect('example.db')
      cursor = conn.cursor()
      cursor.execute("SELECT * FROM data_table")
      rows = cursor.fetchall()
      conn.close()
  
      data = {}
      for row in rows:
          data[row[0]] = row[1]
  
      return json.dumps(data)