serialize_matrix — Serialize a matrix.
serialize_matrix serializes the data of a matrix (see
fwrite_serialized_item for an introduction of the basic
principle of serialization). The same data that is written in a
write_matrix is converted to a serialized item.
The matrix is defined by the handle
serialized matrix is returned by the handle
SerializedItemHandle and can be deserialized by
Handle of the serialized item.
If the parameters are valid, the operator
serialize_matrix returns the value 2 (H_MSG_TRUE). If
necessary, an exception is raised.