nomer repeat units of which have at least one photosensitivity-imparting group thereon, said polymer having a first degree of photosensitivity-imparting group substitution measured in milliequivalents of photosensitivity-imparting group per gram and being of the general formula wherein x is an integer of 0 or 1, A is one of several specified groups, such as B is one of several specified groups, su