How to use the xstream.fromPromise function in xstream

.map(() =>
        xs.fromPromise(
          PermissionsAndroid.request(
            PermissionsAndroid.PERMISSIONS.ACCESS_COARSE_LOCATION,
            {
              title: 'Allow locating via Bluetooth?',
              message:
                'Manyverse needs to use Bluetooth to discover where you are ' +
                '("coarse location") and what peers are around you.',
              buttonPositive: 'Yes',
              buttonNegative: 'No',
            },
          ),
        ),
      )

      .map(([token]) => xs.fromPromise(this.userAdapter.setUserFromIdentityToken(token)))
      .flatten()

.map(([page, limit]) =>
        xs.fromPromise(this.userAdapter.getBlockedUser(page, limit))
      )

      .map(promise => xs.fromPromise(promise))
      .flatten();

.map(username =>
            xs.fromPromise(
                fetch(`https://api.github.com/users/${username}`).then(res =>
                    res.json()
                )
            )
        )

public showPicker(
    title?: string,
    content?: string,
    options?: OptionsPicker,
  ): Stream {
    return xs.fromPromise(DialogAndroid.showPicker(title, content, options));
  }

.map(({ roomId, name, avatarUrl, extras }) =>
        xs.fromPromise(this.roomAdapter.updateRoom(roomId, name, avatarUrl, extras))
      )

.map(([userId, userKey, username, avatarUrl, extras]) =>
        xs.fromPromise(
          this.userAdapter.login(userId, userKey, {
            name: username,
            avatarUrl,
            extras
          })
        )
      )

.map(([username, avatarUrl, extras]) =>
        xs.fromPromise(this.userAdapter.updateUser(username, avatarUrl, extras))
      )

.map(([uniqueId, name, avatarUrl, extras]) =>
        xs.fromPromise(this.roomAdapter.getChannel(uniqueId, name, avatarUrl, extras))
      )