get credentials() {
    switch (this.authMethod) {
      case "iam": // explicit credentials
        return {
          accessKeyId: process.env.AWS_BEDROCK_LLM_ACCESS_KEY_ID,
          secretAccessKey: process.env.AWS_BEDROCK_LLM_ACCESS_KEY,
        };
      case "sessionToken": // Session token is used for temporary credentials
        return {
          accessKeyId: process.env.AWS_BEDROCK_LLM_ACCESS_KEY_ID,
          secretAccessKey: process.env.AWS_BEDROCK_LLM_ACCESS_KEY,
          sessionToken: process.env.AWS_BEDROCK_LLM_SESSION_TOKEN,
        };
      // IAM role is used for long-term credentials implied by system process
      // is filled by the AWS SDK automatically if we pass in no credentials
      case "iam_role":
        return {};
      default:
        return {};
    }
  }
Gets the credentials for the AWS Bedrock LLM based on the authentication method provided.
@returns {object} The credentials object.