code: def _is_collinear(self, lons, lats):
          
  
          x, y, z = lonlat2xyz(lons[:3], lats[:3])
          pts = np.column_stack([x, y, z])
  
          collinearity = (np.linalg.det(pts.T) == 0.0)
  
          return collinearity
docs: Checks if first three points are collinear - in the spherical
          case this corresponds to all points lying on a great circle
          and, hence, all coordinate vectors being in a single plane.