need help with Common Lisp program:

TODO Define the function left-shift of a list of digits. Beware! This is a traditional left-shift, which means it's equivalent to multiplying by 2. But since we write numbers with the least-significant bit first, we actually shift to the right. (See unit tests below to make you understand the last sentence.) The name is consistent with the shift operation in computers (defun left-shift (1) TODO ;; Here are some unit tests for left-shift. Add at least two more. (0 1 0 0)) (0 1 0)) (0 1 (check-expect (left-shift . (1 0 0)) check-expect (left-shift (1 0)) heck-expect (left-shift (1 e e e 0)) e 0 0)1