/etc/bash_completion.d/optcomplete is in python-optcomplete 1.2-13.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 | #!/bin/sh
#
# $Id: optcomplete.bash,v 1.6 2004/01/26 06:24:48 blais Exp $
# $Source: /u/blais/cvsroot/optcomplete/etc/optcomplete.bash,v $
#
# optcomplete harness for bash shell. You then need to tell 
# bash to invoke this shell function with a command like 
# this::
#
#   complete -F _optcomplete optcomplete-test
#
_optcomplete()
{
    COMPREPLY=( $( \
	COMP_LINE=$COMP_LINE  COMP_POINT=$COMP_POINT \
	COMP_WORDS="${COMP_WORDS[*]}"  COMP_CWORD=$COMP_CWORD \
	OPTPARSE_AUTO_COMPLETE=1 $1 ) )
}
 |