def add_role role
      raise ArgumentError, '#add_role takes a single role String or Symbol as the argument' if !role || role.kind_of?(Array)
      add_roles role
    end
def add_role role
      raise ArgumentError, '#add_role takes a single role String or Symbol as the argument' if !role || role.kind_of?(Array)
      add_roles role
    end
add a single role