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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 itertrajs(meta, stride=1):
 """Load one mdtraj trajectory at a time and yield it. MDTraj does striding badly. It reads in the whole trajectory and then performs a stride. We join(iterload) to conserve memory. """


    tops = preload_tops(meta)
    for i, row in meta.iterrows():
        yield i, md.join(md.iterload(row['traj_fn'],
                                     top=tops[row['top_fn']],
                                     stride=stride),
                         discard_overlapping_frames=False,
                         check_topology=False)