toString() results in wrong formatting for first attribute

[Guseyn]

If I initially have such html:

<button
   data-primary
   ...other attributes
</button>

Then after parsing and calling toString(), it results into:

<button                 data-primary
  ...other attributes
</button>

If I initially have first attribute on the same line as tag name, then it works fine. Sometimes, I prefer to have first attribute on new line but it gets ruined like I showed above.