code: def _init_defaults(self):
          
          defaults = {
              'build_dir': None,
              'build_datetime': datetime.datetime.now(dateutil.tz.tzutc()),
              'pdf_path': None,
              'extra_downloads': list(),
              'environment': None,
              'lsstdoc_tex_path': None,
              'title': None,
              'title_plain': "",
              'authors': None,
              'authors_json': list(),
              'doc_handle': None,
              'series': None,
              'series_name': None,
              'abstract': None,
              'abstract_plain': "",
              'ltd_product': None,
              'docushare_url': None,
              'github_slug': None,
              'git_branch': 'master',  # so we default to the main LTD edition
              'git_commit': None,
              'git_tag': None,
              'travis_job_number': None,
              'is_travis_pull_request': False,  # If not on Travis, not a PR
              'is_draft_branch': True,
              'aws_id': None,
              'aws_secret': None,
              'keeper_url': 'https://keeper.lsst.codes',
              'keeper_user': None,
              'keeper_password': None,
              'upload': False
          }
          return defaults
docs: Create a `dict` of default configurations.