def simple?
      return false if keys.size > SimpleQueryMaxSize
      key_set = keys.to_set
      key_set == SimpleIdQueryKeys || key_set == SimpleIdAndTypeQueryKeys
    end
def simple?
      return false if keys.size > SimpleQueryMaxSize
      key_set = keys.to_set
      key_set == SimpleIdQueryKeys || key_set == SimpleIdAndTypeQueryKeys
    end
Public: The definition of simple is querying by only _id or _id and _type.
 If this is the case, you can use IdentityMap in library to not perform
 query and instead just return from map.

 Returns true or false