old_contents: from django import template
  from django.template import Library
  register = Library()
  from django.utils.safestring import mark_safe
  
  @register.filter(name="to_queries")
  def to_queries(value):
      """Compiles search queries from keywords"""
      
      li = []
      kws = value.split(',')
      for kw in kws:
          li.append('<a href="/search?q=%s">%s</a>' % (kw, kw))
      
      output = ', '.join(li)
      return mark_safe(output)
new_contents: from django import template
  from django.template import Library
  register = Library()
  from django.utils.safestring import mark_safe
  import os
  
  @register.filter(name="to_queries")
  def to_queries(value):
      """Compiles search queries from keywords"""
      
      li = []
      kws = value.split(',')
      for kw in kws:
          li.append('<a href="/search?q=%s">%s</a>' % (kw, kw))
      
      output = ', '.join(li)
      return mark_safe(output)
      
  @register.filter(name="ext")
  def ext(path):
      """ Returns the extension"""
      try:
          s = os.path.splitext(path)[1].replace('.','')
      except:
          s = None
          
      return s
subject: add extension filter