Are there only two allowed orders of degrees of freedom, that depend on `parameters.reorder_serial_dofs=True/False`

, in the case of a three-dimensional vector function space?

More precisely, for a three-dimensional vector field m (with components mx1, my1, and mz1 at mesh node 1, components mx2, my2, and mz2 at mesh node 2, etc.) with `parameters.reorder_serial_dofs=True`

, the order of degrees of freedom `m.vector().array()`

is:

[mx1, my1, mz1, mx2, my2, mz2, mx3, my3, mz3, ….],

where vector components at every mesh node are grouped together. On the other hand, if `parameters.reorder_serial_dofs=False`

, the order does not assume that vector components at every node are grouped together, but it becomes:

[mx1, mx2, mx3, … my1, my2, my3, … mz1, mz2, mz3, …]

where values of a single vector component at all mesh nodes are grouped together.

These two orders can be seen by changing the `parameters.reorder_serial_dofs=True/False`

in the following code:

```
import dolfin as df
df.parameters.reorder_dofs_serial = True
mesh = df.IntervalMesh(4, 1, 5)
fspace = df.VectorFunctionSpace(mesh, 'CG', 1, 3)
expression = df.Expression(['x[0]+0.1', 'x[0]+0.2', 'x[0]+0.3'])
f = df.interpolate(expression, fspace)
print f.vector().array()
```

The expression in this code is chosen so that the number before the decimal point denotes the mesh node and a number after the decimal point determines the component of a vector field.

For `reorder_dofs_serial=True`

, I get:

[ 5.1 5.2 5.3 4.1 4.2 4.3 3.1 3.2 3.3 2.1 2.2 2.3 1.1 1.2 1.3]

and for `reorder_dofs_serial=False`

, I obtain:

[ 1.1 2.1 3.1 4.1 5.1 1.2 2.2 3.2 4.2 5.2 1.3 2.3 3.3 4.3 5.3]

The question is: Are there any cases with neither of these two orders?