function getOperator(obj, args) {
  let operator = flag(obj, 'operator');
  let negate = flag(obj, 'negate');
  let expected = args[3];
  let msg = negate ? args[2] : args[1];

  if (operator) {
    return operator;
  }

  if (typeof msg === 'function') msg = msg();

  msg = msg || '';
  if (!msg) {
    return undefined;
  }

  if (/\shave\s/.test(msg)) {
    return undefined;
  }

  let isObject = isObjectType(expected);
  if (/\snot\s/.test(msg)) {
    return isObject ? 'notDeepStrictEqual' : 'notStrictEqual';
  }

  return isObject ? 'deepStrictEqual' : 'strictEqual';
}
### .getOperator(message)

Extract the operator from error message.
Operator defined is based on below link
https://nodejs.org/api/assert.html#assert_assert.

Returns the `operator` or `undefined` value for an Assertion.

@param {object} obj object (constructed Assertion)
@param {unknown} args chai.Assertion.prototype.assert arguments
@returns {unknown}
@namespace Utils
@name getOperator
@public