ecerr_source_encoding 4562 transcode.c        rb_define_method(rb_eUndefinedConversionError, "source_encoding", ecerr_source_encoding, 0);
ecerr_source_encoding 4568 transcode.c        rb_define_method(rb_eInvalidByteSequenceError, "source_encoding", ecerr_source_encoding, 0);