This is a helper function that checks the validity of ``params``
        dictionary by matching it with ``allowed_params`` of a ``func``
        attribute, and then performs a call.  Will issue a
        ``wepay.exceptions.WePayWarning`` in case of unrecognized parameter, and
        raise a `WePayError` after making a call, in case if it is in fact
        unrecognized.  If ``batch_mode`` is set to ``True`` instead of making a
        call it will construct a dictionary that is ready to be used in
        :func:`WePay.batch.create` later on, while ``refernce_id`` can also be
        added to it later, as specified by WePay Documentation, see
        :meth:`batch.create<wepay.calls.batch.Batch.create>`

        :param func callable: function making the call
        :param dict params: parameters to include in the call
        :param dict extra_kwargs: extra kwargs passed to a call
        :returns: dict -- depending on ``batch_mode`` flag, either WePay response 
            through calling :func:`call` or a dictionary that is ready 
            to be appended to ``calls`` list that is passed to 
            :meth:`batch.create<wepay.calls.batch.Batch.create`>
        :raises: :exception:`wepay.exceptions.WePayError`

def make_call(self, func, params, extra_kwargs):
        """This is a helper function that checks the validity of ``params``
        dictionary by matching it with ``allowed_params`` of a ``func``
        attribute, and then performs a call.  Will issue a
        ``wepay.exceptions.WePayWarning`` in case of unrecognized parameter, and
        raise a `WePayError` after making a call, in case if it is in fact
        unrecognized.  If ``batch_mode`` is set to ``True`` instead of making a
        call it will construct a dictionary that is ready to be used in
        :func:`WePay.batch.create` later on, while ``refernce_id`` can also be
        added to it later, as specified by WePay Documentation, see
        :meth:`batch.create<wepay.calls.batch.Batch.create>`

        :param func callable: function making the call
        :param dict params: parameters to include in the call
        :param dict extra_kwargs: extra kwargs passed to a call
        :returns: dict -- depending on ``batch_mode`` flag, either WePay response 
            through calling :func:`call` or a dictionary that is ready 
            to be appended to ``calls`` list that is passed to 
            :meth:`batch.create<wepay.calls.batch.Batch.create`>
        :raises: :exception:`wepay.exceptions.WePayError`

        """
        if hasattr(func, '__name__'):
            uri = '/%s/%s' % (self.call_name, func.__name__[2:])
        else:
            uri = '/%s' % self.call_name
        control_kwargs = self._update_params(
            params, extra_kwargs, getattr(func, 'control_keywords', None))
        if not self._api.silent:
            unrecognized_params = set(params) - set(func.allowed_params)
            if unrecognized_params:
                err_msg = (
                    "At least one of the parameters to the api call: '%s' is "
                    "unrecognized. Allowed parameters are: '%s'. Unrecognized "
                    "parameters are: '%s'." % (uri, ', '.join(func.allowed_params), 
                                               ', '.join(unrecognized_params)))
                if self._api.production and self._api.silent is None:
                    warnings.warn(err_msg, WePayWarning)
                else:
                    raise WePayWarning(err_msg)
        
        # in case if param is Decimal
        for name in self.floating:
            if name in params:
                params[name] = float(params[name])
        if control_kwargs.pop('batch_mode', False):
            call = {
                'call': uri
            }
            access_token = control_kwargs.get('access_token', None)
            if access_token is not None:
                call['authorization'] = access_token
            if params:
                call['parameters'] = params
            if control_kwargs.get('reference_id', None) is not None:
                call['reference_id'] = control_kwargs['reference_id']
            return call
        return self._api.call(uri, params=params, **control_kwargs)