Material Name in convert_to_multigroup; Elements vs. Attributes

[yrrepy]

Bug Description

convert_to_multigroup only accepts name on the first line. As an attribute Not models where it is a sub-element.

I believe the material id has similar issues.

Good

    <material id="1" name="PNNL Air">
      <density units="g/cm3" value="0.001205"/>
      <nuclide ao="1" name="C12"/>
      <nuclide ao="1" name="C13"/>
      <nuclide ao="1" name="O16"/>
      <nuclide ao="1" name="Ar40"/>
    </material>

Bad

    <material id="1">
      <name>PNNL Air</name>
      <density units="g/cm3" value="0.001205"/>
      <nuclide ao="1" name="C12"/>
      <nuclide ao="1" name="C13"/>
      <nuclide ao="1" name="O16"/>
      <nuclide ao="1" name="Ar40"/>
    </material>

Both forms should work.

Steps to Reproduce

use openmc.model.convert_to_multigroup on a model that has been read in by the Python API that contains a material card in the Bad form above.

Environment

WSL Ubuntu OpenMC 0.15.3-dev9 Compiled from source OpenMC Official ENDF80 nuclear data