The response message for
[Versions.ListVersions][google.cloud.dialogflow.cx.v3.Versions.ListVersions].
Attributes:
versions (Sequence[google.cloud.dialogflowcx_v3.types.Version]):
A list of versions. There will be a maximum number of items
returned based on the page_size field in the request. The
list may in some cases be empty or contain fewer entries
than page_size even if this isn't the last page.
next_page_token (str):
Token to retrieve the next page of results,
or empty if there are no more results in the
list.