docs: def hat_map(vec):
      """Return that hat map of a vector
      
      Inputs: 
          vec - 3 element vector
  
      Outputs:
          skew - 3,3 skew symmetric matrix
  
      """
      vec = np.squeeze(vec)
      skew = np.array([
                      [0, -vec[2], vec[1]],
                      [vec[2], 0, -vec[0]],
                      [-vec[1], vec[0], 0]])
  
      return skew