Ruby on Rails 4: options value in form_for helper

I want to make a helper for the bootstrap, and for controls (text_field,
label …) I need to use the options of the form_for. There is a form

<%= form_for(@user, url: signup_path, layout: :horizontal) do |user_f|
%> <%= user_f.fields_for :person do |person_f| %> <%=
person_f.text_field(:last_name) %> <%= person_f.options %> <% end %> <%=
user_f.text_field(:last_name) %> <%= user_f.options %> <% end %>

I need to get the value :layout in the control from the form_for I do
not
understand why <%= user_f.options %> displays:

{:url=>"/signup?locale=ru", :layout=>:horizontal,
:html=>{:class=>“new_user”, :id=>“new_user”, :method=>:post,
:authenticity_token=>nil}}

And <%= person_f.options %> displays:

{:builder=>nil, :namespace=>nil,
:parent_builder=>#<ActionView::Helpers::FormBuilder:0x007fd338058c60
@nested_child_index={}, @options={:url=>"/signup?locale=ru",
:layout=>:horizontal, :html=>{:class=>“new_user”, :id=>“new_user”,
:method=>:post, :authenticity_token=>nil}},
@template=#<#Class:0x007fd338030738:0x007fd3375e2268 @_routes=nil,
@_config={}, @view_renderer=#<ActionView::Renderer:0x007fd3375e2510
@lookup_context=#<ActionView::LookupContext:0x007fd3375d31a0
@details_key=#<ActionView::LookupContext::DetailsKey:0x007fd3371da5f8
@hash=-3796700121417373084>, @details={:locale=>[:ru],
:formats=>[:html], :handlers=>[:erb, :builder, :raw, :ruby, :jbuilder]},
@skip_default_locale=false, @cache=true, @prefixes=[“signup”,
“application”], @rendered_format=:html,
@view_paths=#<ActionView::PathSet:0x007fd3375d3970
@paths=[#<ActionView::OptimizedFileSystemResolver:0x007fd33720f3e8
@pattern=":prefix/:action{.:locale,}{.:formats,}{.:handlers,}",
@cache=#<ActionView::Resolver::Cache:0x007fd33720f3c0
@data=#<ActionView::Resolver::Cache::SmallCache:0x007fd33720f398
@backend={#<ActionView::LookupContext::DetailsKey:0x007fd3371da5f8
@hash=-3796700121417373084>=>#<ActionView::Resolver::Cache::SmallCache:0x007fd3371d9810
@backend={“new”=>#<ActionView::Resolver::Cache::SmallCache:0x007fd3371d96d0
@backend={“signup”=>#<ActionView::Resolver::Cache::SmallCache:0x007fd3371d9540
@backend={false=>#<ActionView::Resolver::Cache::SmallCache:0x007fd3371d9450
@backend={[]=>[app/views/signup/new.html.erb]}, @default_proc=nil>},
@default_proc=#<Proc:0x007fd33438afe0@/Users/NikolayLipovtsev/.rvm/gems/ruby-2.0.0-p353/gems/actionpack-4.0.2/lib/action_view/template/resolver.rb:45
(lambda)>>},
@default_proc=#<Proc:0x007fd33438afb8@/Users/NikolayLipovtsev/.rvm/gems/ruby-2.0.0-p353/gems/actionpack-4.0.2/lib/action_view/template/resolver.rb:46
(lambda)>>,

…and there is more still large hash. As well that the form options
contains much information?

How I can get :layout from person_f and user_f?