@classmethod
def merge(cls, root_dir, year, fn_out, job_frac_map):
    """Merge multiple DPV reV runs into a single result based on fractional
        contributions.

        Parameters
        ----------
        root_dir : str
            Root directory containing sub directories containing reV dpv job
            files.
        year : int | str
            Year of interest.
        fn_out : str
            Filename for merged results, to be saved in root_dir.
        job_frac_map : dict
            Lookup of the fractional contribution for each job.
            The keys are job names (string tags found in the sub_dirs and
            job h5 files), and the values are fractions for the
            respective jobs.
        """
    dpv = cls(root_dir, year, sub_dirs=list(job_frac_map.keys()))
    dpv._merge_dpv_files(fn_out, job_frac_map)
