why not check the column order and type consistent before use ‘appand’ mode in to_csv or equivalent ops such as to_sql?
as the title say, when i append a column permutation of a exists dataframe to a exists(saved)
csv file, the column permutation df not reordered by the exist header in csv file.
one reason i can understand is that not all csv file have header in the first row, so 
this design seems reasonable, but for many cases, if the source code reordered for
our append op which have header or table column, this may be more convenient.
same problem to type.