docs: def _make_A_and_part_of_b_adjacent(self, ref_crds):
          """
          Make A and part of b. See docstring of this class
          for answer to "What are A and b?"
          """
          rot = self._rotate_rows(ref_crds)
          A = 2*(rot - ref_crds)
          partial_b = (rot**2 - ref_crds**2).sum(1)
          return A, partial_b