For an object like this:
const type_tags = {
'Academic': ['science'],
'Tech Conference': [],
'Documentary': ['documentary'],
'Historical': []
};
You may want to flatten this in the reverse, which requires the flattening of a list of tuples.
To do this, you first need to create the tuples, reverse them, and flatten them, like so:
_.fromPairs(
_.flatMap(
type_tags,
(k, v) =>
k.map(
key => [key, v]
)
)
)