'Check the dude out:'

def doExpressCheckoutPayment(self, params):

    if ('amt' in params):
        import warnings
        warnings.warn("'amt'    has    been    deprecated.    'paymentrequest_0_amt'    should    be    used    instead.", DeprecationWarning)
        params = params.copy()
        params.update({'paymentrequest_0_amt': params['amt']})
        del params['amt']
    defaults = {'method': 'DoExpressCheckoutPayment', 'paymentaction': 'Sale'}
    required = ['returnurl', 'cancelurl', 'paymentrequest_0_amt', 'token', 'payerid']
    nvp_obj = self._fetch(params, required, defaults)
    if nvp_obj.flag:
        raise PayPalFailure(nvp_obj.flag_info)
    payment_was_successful.send(sender=nvp_obj, **params)
    return nvp_obj
