literal.py

from typing import Literal

def set_environment(env: Literal["development", "staging", "production"]) -> str:
    return f"Environment set to {env}"

print(set_environment("development"))  # Output: Environment set to development
print(set_environment("production"))  # Output: Environment set to production

# The following would raise a type error with a type checker like mypy, as "test" is not a valid literal
# print(set_environment("test"))