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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 merge_sketches(outdir, sketch_paths):
 """Merge new Mash sketches with current Mash sketches Args: outdir (str):
 output directory to write merged Mash sketch file sketch_paths (list of str):
 Mash sketch file paths for input fasta files Returns: str: output path for Mash sketch file with new and old sketches """

    merge_sketch_path = os.path.join(outdir, 'sistr.msh')
    args = ['mash', 'paste', merge_sketch_path]
    for x in sketch_paths:
        args.append(x)
    args.append(MASH_SKETCH_FILE)
    logging.info('Running Mash paste with command: %s', ' '.join(args))
    p = Popen(args)
    p.wait()
    assert os.path.exists(merge_sketch_path), 'Merged sketch was not created at {}'.format(merge_sketch_path)
    return merge_sketch_path