the theming of the avatar upload block

Hello Ivan, I have another question regarding the theming of the user personal data editing page and I've encountered a problem: the button for uploading an avatar, or rather the file upload button, has no styles. The code for it is as follows: <input id="edit-picture-upload" class="form-file" type="file" size="48" name="files[picture_upload]">

Could you please advise on how to fix this issue? Also, I'm curious where this form file is located in the core of Drupal