class LibXML::XML::Namespace

def <=>(other)

considered equal if their prefixes and hrefs are the same.
Compares two namespace objects. Namespace objects are

namespace1 <=> namespace2
call-seq: 
def <=>(other)
  if self.prefix.nil? and other.prefix.nil?
    self.href <=> other.href
  elsif self.prefix.nil?
    -1
  elsif other.prefix.nil?
    1
  else
    self.prefix <=> other.prefix
  end
end