ASAP SD task: enable list, save, restore, delete and rename flag version files
These flag version files are copies of the flag column for a
measurement set. They can be restored to the data set to obtain
a previous flag version. It is wise to
save a flagversion at the beginning or after serious editing.
Keyword arguments:
infile -- Name of input SD dataset
default: ''. example: infile='ngc5921.asap'
mode -- Flag version operation
default: 'list'; to list existing flagtables
'save' will save flag column from infile to a specified flag file
'restore' will place the specified flag file into infile
'delete' will delete specified flag file
'rename' will rename a specified flag file
>>> mode expandable parameters
versionname -- Flag version name
default: none; example: versionname='original_data'
No imbedded blanks in the versionname
comment -- Short description of a versionname, when mode is 'save'
or 'rename'
default: ''; example: comment='Clip above 1.85'
comment = versionname
oldname -- When mode='rename', the flag file to rename
merge -- Merge operation
Options: 'or','and', but not recommended for now.