Interesting, when I run the following Python script I do not see any warnings:
import jmp
import pandas as pd
dt = jmp.open(jmp.SAMPLE_DATA + "Big Class.jmp")
pandas_df = (pd.api.interchange.from_dataframe(dt))
print(pandas_df)
Could you check to see if the error occurs when running the Python from within JMP's Python editor, or if it is specific to Python executed using Python Submit?
I also tried the following at it did not give me an error:
dt = Open( "$SAMPLE_DATA/Big Class.jmp" );
Python Send( dt );
Python Submit( "pandas_df = (pd.api.interchange.from_dataframe(dt))" );
Python Submit( "dt2 = jmp.from_dataframe(pandas_df)" );
Python Get(dt2);
Could you test these scripts to see if they also give the same warning on your end?