[BUG] Unable to convert medit mesh to SU2

[casfra96]

Describe the bug
When I try to convert any medit mesh to SU2 I receive the following error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/meshio/_helpers.py", line 188, in write
    return writer(filename, mesh, **kwargs)
  File "/meshio/su2/_su2.py", line 340, in write
    for index, (cell_type, data) in enumerate(mesh.cells):
TypeError: cannot unpack non-iterable CellBlock object

The error occurs when writing the SU2 mesh. In particular, after having written all the elements of the internal volume, when it has to start writing the surface elements for each tag, the execution stops and gives the error.

I believe the error is not with converting the medit format to SU2 format, just with writing a SU2 mesh.

To Reproduce

Just write a SU2 mesh with any tags.

mesh = meshio.read("input.mesh")
meshio.write("output.su2", mesh)