pyflakes does not seem to take into consideration the typing.no_type_check decorator and throws F821 undefined name error,
Example (from Uplink's documentation, a great library with a custom use case for type annotation):
from uplink import Consumer, get, Path, Query
from typing import no_type_check
class GitHub(Consumer):
    """A Python Client for the GitHub API."""
    @get("users/{user}/repos")
    @no_type_check
    def get_repos(self, user: Path, sort_by: Query("sort")):
        """Get user's public repositories.""" 
Results of running pyflakes:
➜ pyflakes flake8_poc.py
flake8_poc.py:9:52 undefined name 'sort'
 
This raises no error when running using mypy for example.