Merge pull request #238 from hynek/redundant-type-check

Remove redundant check for bytes
diff --git a/OpenSSL/SSL.py b/OpenSSL/SSL.py
index d0cc933..e67bd13 100644
--- a/OpenSSL/SSL.py
+++ b/OpenSSL/SSL.py
@@ -1415,9 +1415,6 @@
         if self._into_ssl is None:
             raise TypeError("Connection sock was not None")
 
-        if not isinstance(buf, bytes):
-            raise TypeError("buf must be a byte string")
-
         result = _lib.BIO_write(self._into_ssl, buf, len(buf))
         if result <= 0:
             self._handle_bio_errors(self._into_ssl, result)
@@ -1898,6 +1895,7 @@
 
         return _ffi.buffer(data[0], data_len[0])[:]
 
+
     @_requires_alpn
     def set_alpn_protos(self, protos):
         """