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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 single_traj_from_n_files(file_list, top):
 """ Creates a single trajectory object from a list of files """

    traj = None
    for ff in file_list:
        if traj is None:
            traj = md.load(ff, top=top)
        else:
            traj = traj.join(md.load(ff, top=top))

    return traj