text: const csv = require('csv-parser');
  const fs = require('fs');
  
  const check_validity = (cardNumber, expiryMonth, expiryYear, cvv, delegate) => {
    var error = {message: "Invalid card"};
    fs.createReadStream('creditCards-mock.csv')
      .pipe(csv({ separator: ';' }))
      .on('data', (row) => {
        if (row["cardNumber"] === cardNumber && row["expiryMonth"] === expiryMonth && row["expiryYear"] === expiryYear && row["cvv"] === cvv){
          error = null;
        }
      })
      .on('end', () => {
        delegate(error, "Valid card");
      });
  }
  
  exports.check_validity = check_validity;