class Nokogiri::XML::NodeSet

def index(node = nil)

Returns the index of the first node in self that is == to +node+ or meets the given block. Returns nil if no match is found.
## 
def index(node = nil)
  if node
    warn("given block not used") if block_given?
    each_with_index { |member, j| return j if member == node }
  elsif block_given?
    each_with_index { |member, j| return j if yield(member) }
  end
  nil
end