code: def dependent_images(self):
          
          found = []
          for command in self.commands:
              dep = command.dependent_image
              if dep:
                  if dep not in found:
                      yield dep
                      found.append(dep)
docs: Determine the dependent images from these commands
  
          This includes all the FROM statements
          and any external image from a complex ADD instruction that copies from another container