docs: def nodes_touching_edge(edge_coord):
      """
      Returns the two node coordinates which are on the given edge coordinate.
  
      :return: list of 2 node coordinates which are on the given edge coordinate, list(int)
      """
      a, b = hex_digit(edge_coord, 1), hex_digit(edge_coord, 2)
      if a % 2 == 0 and b % 2 == 0:
          return [coord_from_hex_digits(a, b + 1),
                  coord_from_hex_digits(a + 1, b)]
      else:
          return [coord_from_hex_digits(a, b),
                  coord_from_hex_digits(a + 1, b + 1)]