class RDoc::TomDoc

def self.signature comment
  return unless comment.tomdoc?
  document = comment.parse
  signature = nil
  found_heading = false
  found_signature = false
  document.parts.delete_if do |part|
    next false if found_signature
    found_heading ||=
      RDoc::Markup::Heading === part && part.text == 'Signature'
    next false unless found_heading
    next true if RDoc::Markup::BlankLine === part
    if RDoc::Markup::Verbatim === part then
      signature = part
      found_signature = true
    end
  end
  signature and signature.text
end