code: def _dump_knitting_pattern(self, file):
          
          knitting_pattern_set = self.__on_dump()
          knitting_pattern = knitting_pattern_set.patterns.at(0)
          layout = GridLayout(knitting_pattern)
          builder = AYABPNGBuilder(*layout.bounding_box)
          builder.set_colors_in_grid(layout.walk_instructions())
          builder.write_to_file(file)
docs: dump a knitting pattern to a file.