Search for Material Nuclides containing just elemental data.

[MicahGale]

Is your feature request related to a problem? Please describe.

Sometimes you get a model with legacy nuclear data, e.g., 26000.50c that you want to replace.
However, if you do problem.materials.get_containing("26000.50c") you will get all iron isotopes.
It's unclear right now if the library extension is being matched (needs verification).

While in some cases this is a nice behavior, its not always the best.

Describe the solution you'd like

I think an strict parameter would be helpful.

So problem.materials.get_containing("26000.50c", strict=True) would exactly match the required nuclide.
This would also be helpful for finding library-less nuclides.

Describe alternatives you've considered

The alternatives might be:

for material in problem.materials:
    for nuclide in material.nuclides:
        if nuclide == "2600.50c": 
             yield material
             break

Additional context
This is for version 1.0.0a1.