TypeError: unique is not a function

Following the first example in the README, I get a TypeError

> TypeError: unique is not a function

Here is the sample file I've created:

**index.js**
```
import unique from 'unique-selector';

const DOM = 'Some text';
const options = {
selectorTypes : [ 'ID', 'Class', 'Tag', 'NthChild' ]
}

console.log(typeof unique, JSON.stringify(unique)); // "object", {}
unique( DOM, options );
```

And here is the full error message

**Error message**
```
TypeError: unique is not a function
at file:///Users/path/to/project/unique-selector-poc/index.js:10:1
at ModuleJob.run (internal/modules/esm/module_job.js:146:23)
at async Loader.import (internal/modules/esm/loader.js:165:24)
at async Object.loadESM (internal/process/esm_loader.js:68:5)
```
**package.json**
```
{
"name": "unique-selector-poc",
"version": "1.0.0",
"main": "index.js",
"license": "MIT",
"dependencies": {
"unique-selector": "0.5.0"
},
"type": "module"
}
```

Please help me identify where I'm going wrong.