Blank Boxes by Column

A club collects sign-up forms as a list of dictionaries, one per form. Some boxes were left blank. A blank box is either the value None, or a key that is missing from that form altogether.

Write missing_percent(replies). Return a dictionary that maps each column to the percentage of forms where that column is blank, rounded to 1 decimal place.

• Only include columns that have at least one blank. A column with no blanks is left out.
• List the columns in the order they first appear across the forms (the order pandas gives the columns when it builds a DataFrame from the list).
• If there are no forms, or no blanks at all, return an empty dictionary.