def find!(target)
      @associations.each do |a|
        return a if a.include? target
      end
      raise InvalidAssociation, "Could not lookup association for: #{target}"
    end
def find!(target)
      @associations.each do |a|
        return a if a.include? target
      end
      raise InvalidAssociation, "Could not lookup association for: #{target}"
    end
Looks up an association by object, link_field, or method.
 Raises an exception if not found