_fetch() {
          const isFilePath = this.reference.startsWith('file:')
          this.reference = (0, (_misc || _load_misc()).removePrefix)(this.reference, 'file:')
          const urlParse = url.parse(this.reference)

          // legacy support for local paths in yarn.lock entries
          const isRelativePath = urlParse.protocol
            ? urlParse.protocol.match(/^[a-z]:$/i)
            : urlParse.pathname
              ? urlParse.pathname.match(/^(?:\.{1,2})?[\\\/]/)
              : false

          if (isFilePath || isRelativePath) {
            return this.fetchFromLocal(this.reference)
          }

          return this.fetchFromLocal().catch(err => this.fetchFromExternal())
        }
Get a list of all package names in the dependency graph.