function `VectorProjection` not found in module `nbodykit.transform`

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Hi, I'm trying to add RSD to data following an example of the guide of nbodykit
https://nbodykit.readthedocs.io/en/latest/catalogs/common-operations.html#Adding-Redshift-space-Distortions
when I encounter an error:

# apply RSD along the z axis
line_of_sight = [0,0,1]

# redshift and cosmology
redshift =  0.55; cosmo = cosmology.Cosmology(h=0.7).match(Omega0_m=0.31)

# the RSD normalization factor
rsd_factor = (1+redshift) / (100 * cosmo.efunc(redshift))

# update Position, applying RSD
src['Position'] = src['Position'] + rsd_factor * transform.VectorProjection(src['Velocity'], line_of_sight)

AttributeError: module 'nbodykit.transform' has no attribute 'VectorProjection'

So I check the source code of transform.py but find no VectorProjection function. At first, I think maybe this function has been renamed or moved into another module. Unfortunately, there is no information about VectorProjection either in changelog or in issues, and I find it still belongs to transform and remains unchanged in the official documentation.

So I'm wondering if VectorProjection has been removed or what? I'm using the latest 0.3.15 version of nbodykit.