Update ir.py

Author: BobTheBuidler

mypyc/test-data/fixtures/ir.py

@@ -122,6 +122,7 @@ def rpartition(self, sep: str, /) -> Tuple[str, str, str]: ...
     def removeprefix(self, prefix: str, /) -> str: ...
     def removesuffix(self, suffix: str, /) -> str: ...
     def islower(self) -> bool: ...
+    def count(self, substr: str, start: Optional[int] = None, end: Optional[int] = None) -> int: pass
 
 class float:
     def __init__(self, x: object) -> None: pass