code: def setup_method(self):
      self.test_username = "test_username"
      self.test_channel = "#test_slack_channel"
      self.test_text = "test_text"
      self.test_icon_url = "test_icon_url"
      self.test_attachments = [
          {
              "fallback": "Required plain-text summary of the attachment.",
              "color": "#36a64f",
              "pretext": "Optional text that appears above the attachment block",
              "author_name": "Bobby Tables",
              "author_link": "http://flickr.com/bobby/",
              "author_icon": "http://flickr.com/icons/bobby.jpg",
              "title": "Slack API Documentation",
              "title_link": "https://api.slack.com/",
              "text": "Optional text that appears within the attachment",
              "fields": [
                  {
                      "title": "Priority",
                      "value": "High",
                      "short": "false",
                  }
              ],
              "image_url": "http://my-website.com/path/to/image.jpg",
              "thumb_url": "http://example.com/path/to/thumb.png",
              "footer": "Slack API",
              "footer_icon": "https://platform.slack-edge.com/img/default_application_icon.png",
              "ts": 123456789,
          }
      ]
      self.test_blocks = [
          {
              "type": "section",
              "text": {
                  "text": "A message *with some bold text* and _some italicized text_.",
                  "type": "mrkdwn",
              },
              "fields": [
                  {"type": "mrkdwn", "text": "High"},
                  {
                      "type": "plain_text",
                      "emoji": True,
                      "text": "String",
                  },
              ],
          }
      ]
      self.test_attachments_in_json = json.dumps(self.test_attachments)
      self.test_blocks_in_json = json.dumps(self.test_blocks)
      self.test_api_params = {"key": "value"}
  
      self.expected_method = "chat.postMessage"
      self.expected_api_params = {
          "channel": self.test_channel,
          "username": self.test_username,
          "text": self.test_text,
          "icon_url": self.test_icon_url,
          "attachments": self.test_attachments_in_json,
          "blocks": self.test_blocks_in_json,
      }
  
imports: from __future__ import annotations
  import json
  from unittest import mock
  from unittest.mock import MagicMock
  import pytest
  from airflow.exceptions import AirflowProviderDeprecationWarning
  from airflow.providers.slack.operators.slack import SlackAPIFileOperator, SlackAPIOperator, SlackAPIPostOperator
label_desc: Use image node_id 1 for calling the TestSlackAPIPostOperator obj's underlying member method code with example usage: obj.setup_method() without return types