"""Returns the skew-symmetric matrix of a 3D vector.

The skew-symmetric matrix is a 3x3 matrix constructed from the input vector such that it satisfies the properties of a skew-symmetric matrix (i.e., the matrix is equal to the negative of its transpose). This is commonly used in vector cross product operations and in representing angular velocities in 3D space.

Args:
    v (numpy.ndarray): A 3D vector of shape (3,) or (3, 1). The vector should contain numerical values.

Returns:
    numpy.ndarray: A 3x3 skew-symmetric matrix of type float64, constructed from the input vector.
"""
You should write code starting with:
import numpy as np

def skew(v: np.ndarray) -> np.ndarray:
    # TODO: Implement this function
    pass

