Hello,
Just to make sure you're keeping busy, a new issue ;-)

I'm trying to retrieve raw messages for particular receivers. As an example:

from datetime import datetime, timedelta
from traffic.data import opensky

data = opensky.extended(start=start_time,
                        stop=start_time + timedelta(seconds=1),
                        serials=[80391799, 1806596070] )

This produces an error saying that mintime is ambiguous. I guess this is because both the rollcall_replies_data4 table and the rollcall_replies_data4.sensors.item array contain mintime.

On my local copy of traffic I have resolved this by changing line 1073 of opensky_impala.py to this:

columns = (table_name + ".mintime, " +
           table_name + ".maxtime, " +
           table_name + ".rawmsg, " + 
           table_name + ".msgcount, " +
           table_name + ".icao24, " +
           table_name + ".hour")
orig_columns = columns

And then adding the following on line 1023 (just before df = self_format_dataframe(df)):

colnames = {}
ocols = orig_columns.split(',')
for col in ocols:
   tcol = col.lstrip().rstrip()
   pos = tcol.find('.')
   colnames[tcol] = tcol[pos+1:]
df.rename(columns=colnames, inplace=True)

This works for my particular case, but I do not know if this will break some other use of traffic, and it is also maybe not so elegant. Therefore I raise an issue rather than making a PR.
If the above changes are OK to you then I'll make a PR instead, otherwise I can leave it to you to determine the best solution :-)