Of course, please replace EVERYTHING in angle brackets (e.g. "<205/206>") with the information for your section. I teach multiple courses, so this is a general template.
Subject: [PHY<205/206> lab] Request to Attend Your Section
Hello <TA Name>,
I take section <#> of physics <205/206> lab with TA Zain Kamal (CC'd). I'm unable to attend this week, so I was reaching out to ask if I could attend your section on <day of week, time>.
Thank you,
<your name>
<your email>
<your RUID>