ModuleNotFoundError: No module named 'google_vertex_haystack'

[maxim-lixakov]

Describe the bug
I try to install and use VertexAIGeminiGenerator following official documentation but in both cases (running code in prepared colab notebook and both locally in jupyter notebook it fails with error ModuleNotFoundError: No module named 'google_vertex_haystack' when I try to import class: from google_vertex_haystack.generators.gemini import VertexAIGeminiGenerator

To Reproduce
even official example fails with this error (you can see it on screens below):

ensure that package exists:

try to import:

Describe your environment (please complete the following information):

• OS: google colab / IOS Mac M1
• Haystack version:

 google-vertex-haystack             4.0.1
 haystack-ai                        2.8.0
 haystack-experimental              0.4.0

• Integration version: