AWS SES sendEmail(…).promise().then(…) TypeError: Cannot read property ‘then’ of undefined

using node v14.18.1

sesLib is an import.const sesLib = new AWS.SESV2({ ...}) is defined elsewhere

From MDN documentation:

The then() method returns a Promise. It takes up to two arguments:
callback functions for the success and failure cases of the Promise.

I am using the SendEmail feature in AWS SES using with .promise() method to test for empty/null values in the To email address field

original code

const sendEmailImpl = (other_params, sesLib) => {
const params = { ... };
return sesLib.sendEmail(params).promise();
};

I tried the following code, all different variations but they result in the message – Cannot read property ‘then’ of undefined

const sendEmailImpl = (other_params, sesLib) => {
const params = { ... };
return sesLib.sendEmail(params).promise()
    .then((data) => {
      console.log(data)
      resolve(data); // tried with & without resolve statement
  })
  .catch((err) => {
    console.log('error', JSON.stringify(err));
    reject(
      'error', JSON.stringify(err); // tried with & without reject statement
    );
    throw new Exception(...);
  });
};

const sendEmailImpl = async (other_params, sesLib) => {
...
  const params = { ... };
  var sendEmailPromise = await sesLib.sendEmail(params).promise();
  sendEmailPromise.then((ok) => {
    return ok;
  })
  .catch((err) => {
    console.log('error', JSON.stringify(err));
    reject(
      'error', JSON.stringify(err); // tried with & without reject statement
    );
    throw new Exception(...);
  });
};

After running npm test and jest, it always returns the following error

TypeError: Cannot read property 'then' of undefined
...
sesLib.sendEmail(params).promise()
^
.then((data) => {
...

AWS Doc about promises
https://aws.amazon.com/blogs/developer/support-for-promises-in-the-sdk/
SES SendEmail API
https://docs.aws.amazon.com/ses/latest/APIReference/API_SendEmail.html
https://docs.aws.amazon.com/ses/latest/dg/send-email-concepts-email-format.html