class Nokogiri::XML::Node

def namespace= ns

#add_namespace_definition with a nil prefix argument.
for this node. You probably want #default_namespace= instead, or perhaps
a Namespace added this way will NOT be serialized as an xmlns attribute
"xmlns=" attribute in XML source), as a Namespace object +ns+. Note that
Set the default namespace on this node (as would be defined with an
## 
def namespace= ns
  return set_namespace(ns) unless ns
  unless Nokogiri::XML::Namespace === ns
    raise TypeError, "#{ns.class} can't be coerced into Nokogiri::XML::Namespace"
  end
  if ns.document != document
    raise ArgumentError, 'namespace must be declared on the same document'
  end
  set_namespace ns
end