Proof of proveit.numbers.modular.image_size_indep_of_left_shift theorem

import proveit
theory = proveit.Theory() # the theorem's theory

%proving image_size_indep_of_left_shift

With these allowed/disallowed theorem/theory presumptions (e.g., to avoid circular dependencies), we begin our proof of
image_size_indep_of_left_shift:
(see dependencies)