async getCredentials() {
    if (this.cachedCredentials) {
      // We have already created the credentials object once, so return it.
      return this.cachedCredentials
    }
    const creds = await this.resolveCredentials()

    this.cachedCredentials = {
      accessKeyId: creds.accessKeyId,
      secretAccessKey: creds.secretAccessKey,
      sessionToken: creds.sessionToken,
      accountId: creds.accountId,
      callerUserId: creds.callerUserId,
      callerArn: creds.callerArn,
    }
    return this.cachedCredentials
  }
Fetch credentials directly or using a profile from serverless yml configuration or from the
well known environment variables
@returns {{region: *}}