[HW1] About empty space before and after strings in a table

[yingrui-yang]

Sometimes there could be some empty space after the strings (like "math ") in some cells of a table. With this, you might have trouble locating rows using .where(column, are.equal_to("math")) command. It is hard to detect If we just print the whole table or whole column. We should print out the content of the specific cells to identify that.