I already installed haystack on my visual code I used pip install farm-haystack. But I am still getting error when I am importing libraries

Question

Import "haystack.file_converter.pdf" could not be resolved
Import "haystack.document_store.memory" could not be resolved
Import "haystack.retriever.sparse" could not be resolved

I already tried changing my environment to what's compatible to haystack, uninstalling and installing haystack again but still not working, please help me resolve this issue.