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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 _sd_of_eigenvector(data, vec, measurement='poles', bidirectional=True):
 """Unifies ``fit_pole`` and ``fit_girdle``."""

    lon, lat = _convert_measurements(data, measurement)
    vals, vecs = cov_eig(lon, lat, bidirectional)
    x, y, z = vecs[:, vec]
    s, d = stereonet_math.geographic2pole(*stereonet_math.cart2sph(x, y, z))
    return s[0], d[0]