def calc_coordinate(cell_name)
      col = COLUMNS.index(cell_name.slice /[A-Z]+/)
      row = (cell_name.slice /\d+/).to_i - 1 # rows in drawings start with 0
      [row, col]
    end
def calc_coordinate(cell_name)
      col = COLUMNS.index(cell_name.slice /[A-Z]+/)
      row = (cell_name.slice /\d+/).to_i - 1 # rows in drawings start with 0
      [row, col]
    end
Transforms cell name to [row, col], e.g. A1 => [0, 0], B3 => [1, 2]
 Rows and cols start with 0.