/summon villager ~ ~2 ~ {VillagerData:{profession:librarian,level:5,type:plains},Offers:{Recipes:[
{buy:{id:oak_log,Count:64},buyB:{id:oak_sapling,Count:20},sell:{id:wooden_sword,Count:1,tag:{display:{Name:"{\"text\":\"Log Sword\",\"color\":\"dark_green\"}"},AttributeModifiers:
[{AttributeName:"generic.attackDamage",Name:"generic.attackDamage",Amount:5.25,Operation:0,UUIDLeast:111111,UUIDMost:111111,Slot:"mainhand"},
{AttributeName:"generic.attackSpeed",Name:"generic.attackSpeed",Amount:-2.9,Operation:0,UUIDLeast:111111,UUIDMost:111111,Slot:"mainhand"}]
},maxUses:9999999}}]}}

attack speed -3.2 is equal to normal sword speed