def write_reactions(self, stream, reactions, properties=None):
        """Write iterable of reactions as YAML object to stream.

        Args:
            stream: File-like object.
            compounds: Iterable of reaction entries.
            properties: Set of reaction properties to output (or None to output
                all).
        """
        self._write_entries(
            stream, reactions, self.convert_reaction_entry, properties)