def create_reference_msg(msg: ForwardMsg) -> ForwardMsg:
"""Create a ForwardMsg that refers to the given message via its hash.
The reference message will also get a copy of the source message's
metadata.
Parameters
----------
msg : ForwardMsg
The ForwardMsg to create the reference to.
Returns
-------
ForwardMsg
A new ForwardMsg that "points" to the original message via the
ref_hash field.
"""
ref_msg = ForwardMsg()
ref_msg.ref_hash = populate_hash_if_needed(msg)
ref_msg.metadata.CopyFrom(msg.metadata)
return ref_msg
