Error "The frame.append method is deprecated"

I use the following statement to select dataframe columns by chosen input fields in callbacks:

fd4 = fd3.loc[(fd3['YEAR'] == jahr_filter) & (fd3['LAND'] == land2_filter) & (fd3['COUNTS'] != 0)]

Now I receive the following message:

The frame.append method is deprecated and will be removed from pandas in a future version. Use pandas.concat instead.
But I didn’t use the append method in this statement.

Am I wrong and if so how do I have to change the statement?