pub fn copy_destructured(&mut self, r0: &A, r1: &B, r2: &C) {
        unsafe {
            self.local.push(self.inner.copy_destructured(r0, r1, r2));
        }
    }
Copies a destructured tuple `(A, B, C)` into this column stack.

This serves situations where a tuple should be constructed from its constituents but
not all elements are available as owned data.

The element can be read by indexing
differential-dataflow/src/containers.rs