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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 _species_subdir( ensembl_release, species="homo_sapiens", filetype="gtf", server=ENSEMBL_FTP_SERVER):
 """ Assume ensembl_release has already been normalize by calling function but species might be either a common name or latin name. """

    return SPECIES_SUBDIR_TEMPLATE % {
        "release": ensembl_release,
        "filetype": filetype,
        "species": species,
    }