code: def send(self, template, email, _vars=None, options=None, schedule_time=None, limit=None):
          
          _vars = _vars or {}
          options = options or {}
          data = {'template': template,
                  'email': email,
                  'vars': _vars,
                  'options': options.copy()}
          if limit:
              data['limit'] = limit.copy()
          if schedule_time is not None:
              data['schedule_time'] = schedule_time
          return self.api_post('send', data)
docs: Remotely send an email template to a single email address.
          http://docs.sailthru.com/api/send
          @param template: template string
          @param email: Email value
          @param _vars: a key/value hash of the replacement vars to use in the send. Each var may be referenced as {varname} within the template itself
          @param options: optional dictionary to include replyto and/or test keys
          @param limit: optional dictionary to name, time, and handle conflicts of limits
          @param schedule_time: do not send the email immediately, but at some point in the future. Any date recognized by PHP's strtotime function is valid, but be sure to specify timezone or use a UTC time to avoid confusion