code: def separation(self, other):
          r
          dx = other.x - self.x
          dy = other.y - self.y
          return np.hypot(dx, dy)
docs: r"""Separation to another pixel coordinate.
  
          This is the two-dimensional cartesian separation :math:`d` with
  
          .. math::
              d = \sqrt{(x_1 - x_2) ^ 2 + (y_1 - y_2) ^ 2}
  
          Parameters
          ----------
          other : `PixCoord`
              Other pixel coordinate
  
          Returns
          -------
          separation : `numpy.array`
              Separation in pixels