def map_lookup(vers, lookups, injective=False):
    """
    Creates a Map lookup request.

    vers: str
        An arbitrary string assigned by the user. When making updates to an
        existing lookup the value must be lexicographically greater than
        the existing version.
    lookups: dict
        A dictionary of key/value pairs, both of which must be strings.
    injective: bool, default = False
        Marks the lookup as injective, per this reference:
        https://druid.apache.org/docs/latest/querying/lookups.html#query-execution
    """
    return {
        "version": vers,
        "lookupExtractorFactory": {
            "type": "map",
            "injective": injective,
            "map": lookups
            }    
        }