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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 Wget(src_url, tgt_name, tgt_root=None):
 """ Download url, if required. Args: src_url (str):
 Our SOURCE url. tgt_name (str):
 The filename we want to have on disk. tgt_root (str):
 The TARGET directory for the download. Defaults to ``CFG["tmpdir"]``. """

    if tgt_root is None:
        tgt_root = str(CFG["tmp_dir"])

    from benchbuild.utils.cmd import wget

    tgt_file = local.path(tgt_root) / tgt_name
    if not source_required(tgt_file):
        Copy(tgt_file, ".")
        return

    wget(src_url, "-O", tgt_file)
    update_hash(tgt_file)
    Copy(tgt_file, ".")