Change HDF5 file attribute from 'dx,dy,dz' to 'dx_dy_dz'

docs/source/input.rst

@@ -623,7 +623,7 @@ Allows you to insert pre-defined geometry into a model. The geometry is specifie
     * The integer numbers in the HDF5 file correspond to the order of material commands in the materials text file, i.e. if ``#sand: 3 0 1 0`` is the first material in the materials file, it will be associated with any integers that are zero in the HDF5 file.
     * You can use an integer of -1 in the HDF5 file to indicate not to build any material at that location, i.e. whatever material is already in the model at that location.
     * The spatial resolution of the geometry objects must match the spatial resolution defined in the model.
-    * The spatial resolution must be specified as a root attribute of the HDF5 file with the name ``dx, dy, dz`` equal to a tuple of floats, e.g. (0.002, 0.002, 0.002)
+    * The spatial resolution must be specified as a root attribute of the HDF5 file with the name ``dx_dy_dz`` equal to a tuple of floats, e.g. (0.002, 0.002, 0.002)
     * If the geometry objects being imported were originally generated using gprMax, i.e. exported using #geometry_objects_write, then you can use dielectric smoothing as you like when generating the original geometry objects. However, if the geometry objects being imported were generated by an external method then dielectric smoothing will not take place.
 
 For example, to insert a 2x2x2mm^3 AustinMan model with the lower left corner 40mm from the origin of the domain, and using disperive material properties use ``#geometry_objects_read: 0.04 0.04 0.04 ../user_libs/AustinManWoman/AustinMan_v2.3_2x2x2.h5 ../user_libs/AustinManWoman/AustinManWoman_materials_dispersive.txt``