def METHOD_NAME(self, form, fields={}):
    base_fields = self.form_fields_by_ref(form)
    for (key, val) in fields.items():
        base_fields[key] = val
    if 'action' in form.attrib:
        url = self._url(form.attrib['action'])
    else:
        url = self.base_url
    self.post(url, base_fields)