langchain/embeddings/vertexai.py/VertexAIEmbeddings/validate_environment
class VertexAIEmbeddings:    def validate_environment(cls, values: Dict) -> Dict:
        """Validates that the python package exists in environment."""
        cls._try_init_vertexai(values)
        try:
            from vertexai.preview.language_models import TextEmbeddingModel
        except ImportError:
            raise_vertex_import_error()
        values["client"] = TextEmbeddingModel.from_pretrained(values["model_name"])
        return values