code: def _get_default_grid():
      
      s = """
      time,0A 1A,0A   0B,0A   1B,0A
      0A,1A   time,1A 0B,1A   1B,1A
      0A,0B   1A,0B   time,0B 1B,0B
      0A,1B   1A,1B   0B,1B   time,1B
      """.strip()
      dims = [[_ for _ in re.split(' +', line.strip())]
              for line in s.splitlines()]
      return dims
docs: In the grid specification, 0 corresponds to the best channel, 1
      to the second best, and so on. A, B, C refer to the PC components.