Save only the blocks you need?

Question

XSL & XSLT

Good day!
How to save only the necessary blocks from an XML document.
If the block has a specific tag or a tag with a specific value, then keep everything that is included in its parent, if not, then remove it from the selection.
Example:
from this

<document>
<cart>
......
......
   <save>1</save>
......
......
</cart>
<cart>
......
......

......
......
</cart>
</document>

became:

<document>
<cart>
......
......
   <save>1</save>
......
......
</cart>
</document>