numpy 자유자재로 쓰는 고수가 돼야 해
Note that np.dot() performs a matrix-matrix or matrix-vector multiplication. This is different from np.multiply() and the operator (which is equivalent to . in Matlab/Octave), which performs an element-wise multiplication.
난 언제까지 row, column, depth, 차원!! 헷갈려

: 벡터의 norm을 구하거나 벡터를 정규화할 때 사용
-> return : float or ndarray
Norm of the matrix or vector(s).
-> 이렇게 구한 norm으로 각 벡터 나눠 벡터 정규화