trim is a Jinja2 filter used to remove whitespace from the left and right sides of a string. For example, let's say you have the following.

"{{ '     hello world     ' }}"

This should output the following, where we can see whitespace before and after hello world.

"     hello world     "

trim can be used to remove the whitespace from the left and right sides of hello world.

"{{ '     hello world     ' | trim }}"

Which should return the following.

"hello world"