code: def commit_purchase(self, purchaseid, transferid):
          
          return self.request(
              'put',
              safeformat('purchases/{:int}', purchaseid),
              json.dumps({'transferid': transferid})
          )
docs: DECLARES a purchase defined with ``purchaseid`` (bound to vingd transfer
          referenced by ``transferid``) as finished, with user being granted the
          access to the service or goods.
          
          If seller fails to commit the purchase, the user (buyer) shall be
          refunded full amount paid (reserved).
          
          :type purchaseid: ``bigint``
          :param purchaseid:
              Purchase ID, as returned in purchase description, upon
              token/purchase verification.
          :type transferid: ``bigint``
          :param transferid:
              Transfer ID, as returned in purchase description, upon
              token/purchase verification.
          
          :rtype: ``dict``
          :returns:
              ``{'ok': <boolean>}``.
          :raises InvalidData: invalid format of input parameters
          :raises NotFound: non-existing order/purchase/transfer
          :raises GeneralException: depends on details of error
          :raises InternalError: Vingd internal error (network, server, app)
          
          :see: `verify_purchase`.
          :resource: ``purchases/<purchaseid>``
          :access: authorized users (ACL flag: ``type.business``)