pub fn alloc_e(&mut self, constraints: &mut Vec<Constraint>, value: C::EF) -> String {
        let tmp_id = self.alloc_id();
        constraints.push(Constraint {
            opcode: ConstraintOpcode::ImmE,
            args: vec![
                vec![tmp_id.clone()],
                value
                    .as_base_slice()
                    .iter()
                    .map(|x| x.as_canonical_biguint().to_string())
                    .collect(),
            ],
        });
        tmp_id
    }
Allocate an extension element in the constraint system.
crates/recursion/compiler/src/constraints/mod.rs