Values:
IMPORT_OPTION_UNSPECIFIED (0):
Unspecified. Treated as KEEP.
KEEP (1):
Always respect settings in exported flow
content. It may cause a import failure if some
settings (e.g. custom NLU) are not supported in
the agent to import into.
FALLBACK (2):
Fallback to default settings if some settings
are not supported in the agent to import into.
E.g. Standard NLU will be used if custom NLU is
not available.