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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 rmsd(ref_cds, est_cds):
 """ Root-mean-squared-difference """

    ref_dists = pdist(ref_cds)
    est_dists = pdist(est_cds)
    return np.sqrt(((ref_dists - est_dists)**2).mean())