code: def get_build_files_family(project_tree, dir_relpath, build_ignore_patterns=None):
      
      build_files = set()
      for build in sorted(project_tree.glob1(dir_relpath, '{prefix}*'.format(prefix=BuildFile._BUILD_FILE_PREFIX))):
        if BuildFile._is_buildfile_name(build) and project_tree.isfile(os.path.join(dir_relpath, build)):
          build_files.add(os.path.join(dir_relpath, build))
      return BuildFile._build_files_from_paths(project_tree, build_files, build_ignore_patterns)
docs: Returns all the BUILD files on a path