def roles(*roles)
      opts = roles.last.is_a?(Hash) ? roles.pop : {}
      self.valid_roles = roles.flatten.map(&:to_sym)
      unless (opts[:dynamic] == false)
        self.define_dynamic_queries(self.valid_roles)
      end
    end
def roles(*roles)
      opts = roles.last.is_a?(Hash) ? roles.pop : {}
      self.valid_roles = roles.flatten.map(&:to_sym)
      unless (opts[:dynamic] == false)
        self.define_dynamic_queries(self.valid_roles)
      end
    end
:call-seq:
   roles(:role_1, ..., :role_n)
   roles('role_1', ..., 'role_n')
   roles([:role_1, ..., :role_n])
   roles(['role_1', ..., 'role_n'])

 declare valid roles