Format class definitions (#5289)

crates/ruff_python_formatter/src/other/keyword.rs

@@ -1,5 +1,6 @@
-use crate::{not_yet_implemented, FormatNodeRule, PyFormatter};
-use ruff_formatter::{write, Buffer, FormatResult};
+use crate::prelude::*;
+use crate::FormatNodeRule;
+use ruff_formatter::write;
 use rustpython_parser::ast::Keyword;
 
 #[derive(Default)]
@@ -7,6 +8,15 @@ pub struct FormatKeyword;
 
 impl FormatNodeRule<Keyword> for FormatKeyword {
     fn fmt_fields(&self, item: &Keyword, f: &mut PyFormatter) -> FormatResult<()> {
-        write!(f, [not_yet_implemented(item)])
+        let Keyword {
+            range: _,
+            arg,
+            value,
+        } = item;
+        if let Some(argument) = arg {
+            write!(f, [argument.format(), text("=")])?;
+        }
+
+        value.format().fmt(f)
     }
 }