# File lib/capybara/session.rb, line 65
    def fill_in(locator, options={})
      msg = "cannot fill in, no text field, text area or password field with id, name, or label '#{locator}' found"
      raise "Must pass a hash containing 'with'" if not options.is_a?(Hash) or not options.has_key?(:with)
      locate(:xpath, XPath.fillable_field(locator), msg).set(options[:with])
    end