app/views/descriptors/batch_load/modify_gene_descriptor/_form.html.erb
<%= form_tag url, multipart: true do -%>
<div class="field">
<%= label_tag :file, 'Select a file' -%>
<br>
<%= file_field_tag :file -%>
</div>
<%= content_for :warn_level -%>
<%= submit_tag submit, class: ['button-default'] -%>
<% end %>