How can I maintain column headers when adding all sheets to a book?

[unique0ne0]

Hi.

I love to use pyexcel. Thanks.
I have a question.
Just now I realized column headers are gone after some processes with a single sheet, which has column headers assigned by sheet.name_columns_by_row(0).
When I save a file with a single sheet, column headers are ok, but when I save a file as a book after adding, they are gone.

for example..
after inputting header names and data into each sheet..

sheet1.name_columns_by_row(0)
sheet2.name_columns_by_row(0)

sheet1:
+------------+--------+--------+
| column1 | column2| column3 |
+======+======+=====+
| 1 | 2 | 3 |
+------------+--------+--------+

sheet2:
+------------+--------+--------+
| columnA | columnB| columnC |
+======+======+=====+
| A | B | C |
+------------+--------+--------+

book1 = sheet1 + sheet2
book1. save_as(book1_filename)

I naturally thought every sheet in book1 must have column headers, but the result is like below..

sheet1:
+------------+--------+--------+
| 1 | 2 | 3 |
+------------+--------+--------+

sheet2:
+------------+--------+--------+
| A | B | C |
+------------+--------+--------+

when I save each sheet as a separate file, the headers are ok.
So if I use merge_all_to_a_book, it works ok in this case, the headers are not disappeared but this is very complex.
moreover, I have to change sheet names.
This is not a beautiful solution.

Please let me know what I should do to maintain column headers when I add sheets.
I have to use this book at the next process, but it failed because they don't have column names.