def init_defaults(self):
if "<STR_LIT>" not in self:<EOL><INDENT>self['<STR_LIT>'] = "<STR_LIT>" % uuid.uuid1()<EOL><DEDENT>if "<STR_LIT>" not in self:<EOL><INDENT>self['<STR_LIT>'] = datetime.datetime.utcnow().strftime('<STR_LIT>')<EOL><DEDENT>if "<STR_LIT:Content-Type>" not in self:<EOL><INDENT>self['<STR_LIT:Content-Type>'] = WARCHeader.CONTENT_TYPES.get(self.type, "<STR_LIT>")<EOL><DEDENT>
Initializes important headers to default values, if not already specified.

        The WARC-Record-ID header is set to a newly generated UUID.
        The WARC-Date header is set to the current datetime.
        The Content-Type is set based on the WARC-Type header.
        The Content-Length is initialized to 0.