def testAssignByteStringToUnicodeField(self, message_module):
    """Assigning a byte string to a string field should result
    in the value being converted to a Unicode string."""
    m = message_module.TestAllTypes()
    m.optional_string = str('')
    self.assertIsInstance(m.optional_string, str)
Assigning a byte string to a string field should result
    in the value being converted to a Unicode string.
deps/protobuf/python/google/protobuf/internal/message_test.py