def __init__(self, metadata):
self.metadata = metadata<EOL>self.name = metadata.name<EOL>self.key = self.name.lower()    <EOL>self.version = metadata.version<EOL>self.locator = None<EOL>self.digest = None<EOL>self.extras = None      <EOL>self.context = None     <EOL>self.download_urls = set()<EOL>self.digests = {}<EOL>
Initialise an instance.
:param metadata: The instance of :class:`Metadata` describing this
distribution.