import with same alias name in Cython

Question

I am reading pandas source code. Encounter this file

These few lines confused me.

cimport numpy as np
import numpy as np

Sure if this is python, only the second import will be effective and np is pointing to numpy.

My doubts are

1. In Cython, import with same alias, will the first import be valid?
2. Likely it is valid import, then what's difference between cimport and import?
3. As both import with same alias, how the program knows which module it refers to?