Each `inputFromAttrs` is roughly the same function in each class, we
check that the attributes given are correct (in term of keys and other
types) then we coppy the attributes. Instead of having the same code
copied in 10 places, set it in the parent class and specify what is
specific per child class.
Change-Id: If9aecb76cff1e28a1ef6668d83d825686cce8353
Tom Hubrecht
76524b92ee