Need help with FieldTypes import

[Andžej Maciusovič]

In ItemsTableRow.js I see FieldTypes import

import { Columns } from 'FieldTypes';

In EditForm.js I see FieldTypes import

import { Fields } from 'FieldTypes';

Can someone tell me where is this FieldTypes module described ?

I saw there is lib/fieldTypes.js file, but this file not exporting Fields or Columns 

var fields = {
 get AzureFile () { return require('../fields/types/azurefile/AzureFileType'); },
 get Boolean () { return require('../fields/types/boolean/BooleanType'); },
 //... other fields
};


module.exports = fields;

Maybe there is webpack config file? In system.js all mappings described in config file so it easy to figure out paths.