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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_build_file_path(self, build_module) -> str: """Return a full path to the build file of `build_module`. The returned path will always be OS-native, regardless of the format of project_root (native) and build_module (with '/'). """

        project_root = Path(self.project_root)
        build_module = norm_proj_path(build_module, '')
        return str(project_root / build_module /
                   (BUILD_PROJ_FILE if '' == build_module
                    else self.build_file_name))