[Bro] How remove or redefine a field in a log?

[Vito Logrillo]

Hi,
is it possible to remove or redefine an existing field in a log?
For example, if i want to remove only the field

local_orig: bool &log &optional;

in conn.log, how can i do it?
And if i want to redefine it in this way:

local_orig: string &optional &log;

??
Thanks,
Vito