code: def content_item(path1, path2, path_sep='/'):
      
      p1_parts = path1.split(path_sep)
      p2_parts = path2.split(path_sep)
      # special case when path1 is root
      if path1 == path_sep and len(p2_parts) >= 2:
          return p2_parts[1]
      if len(p2_parts) <= len(p1_parts):
          return ''
      for i, item in enumerate(p1_parts):
          if item != p2_parts[i]:
              return ''
      return p2_parts[i+1]
docs: if path1 is subpart of path2, get the next path item.
      example:
      path1 = '/foo'
      path2 = '/foo/bar/foo'
      -> 'bar'