def []=(k, v)
      if RESERVED_FIELDS.include? k.to_sym
        super
      else
        a = self.attributes.find {|a| a.key == k.to_s }
        if(a)
          a.value = v.to_s
        else
          self.attributes << Attribute.new(:key => k.to_s, :value => v.to_s)
        end
      end
    end
def []=(k, v)
      if RESERVED_FIELDS.include? k.to_sym
        super
      else
        a = self.attributes.find {|a| a.key == k.to_s }
        if(a)
          a.value = v.to_s
        else
          self.attributes << Attribute.new(:key => k.to_s, :value => v.to_s)
        end
      end
    end
Set attributes