def field_value(ast, field_name)
      field(ast, field_name).xpath('.//args_add_block//tstring_content
        [count(ancestor::args_add) = 1][count(ancestor::string_add) = 1]
        /@value').map { |a| a.to_s }.last
    end
def field_value(ast, field_name)
      field(ast, field_name).xpath('.//args_add_block//tstring_content
        [count(ancestor::args_add) = 1][count(ancestor::string_add) = 1]
        /@value').map { |a| a.to_s }.last
    end
The value for a specific key in an environment or role ruby file