def __getitem__(self, k):
        """
        C{dirdbm[k]}
        Get the contents of a file in this directory as a string.

        @type k: bytes
        @param k: key to lookup

        @return: The value associated with C{k}
        @raise KeyError: Raised when there is no such key
        """
        if not type(k) == bytes:
            raise TypeError("DirDBM key must be bytes")
        path = self._dnamePath.child(self._encode(k))
        try:
            return self._readFile(path)
        except (EnvironmentError):
            raise KeyError(k)

        C{dirdbm[k]}
        Get the contents of a file in this directory as a string.

        @type k: bytes
        @param k: key to lookup

        @return: The value associated with C{k}
        @raise KeyError: Raised when there is no such key
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/persisted/dirdbm.py