message: This is much cleaner if it's in the Metadata writer itself.
diff: @@ -1695,15 +1695,18 @@ class _Metadata(object):
  Attributes:
  name: The name of the page being described by the Metadata block.
  + version: The source version.
  """
  - def __init__(self, name):
  + def __init__(self, name, version='stable'):
  """Creates a Metadata builder.
  Args:
  name: The name of the page being described by the Metadata block.
  + version: The source version.
  """
  self.name = name
  + self.version = version
  self._content = []
  def append(self, item):
  @@ -1720,6 +1723,7 @@ class _Metadata(object):
  parts = ['<div itemscope itemtype="%s">' % schema]
  parts.append('<meta itemprop="name" content="%s" />' % self.name)
  + parts.append('<meta itemprop="path" content="%s" />' % self.version)
  for item in self._content:
  parts.append('<meta itemprop="property" content="%s"/>' % item)
  