structured_format.pattern-style permissible value creation eg for MIxS

[turbomam]

• vskit expander should support PVs in the MIxS label [id] style #784

I destructively edited src/oaklib/utilities/subsets/value_set_expander.py. I think the real solution will require adding a new permissible value for the pv_formula slot in the metamodel

my idea can be interactively illustrated with

vskit expand --schema mixs_inspired_schema.yaml --output mixs_inspired_schema_expanded.yaml 
linkml-validate --schema mixs_inspired_schema_expanded.yaml --target-class Sample mixs_inspired_data.yaml 

[turbomam]

in support of

• Milestone - Define EnvO value sets for supported environmental extensions (3.2) microbiomedata/issues#468

cc @mslarae13

[cmungall]

This should be done by passing a syntax string like “{label} [{id}]”

• Longer term: add linkmlml metamodel element for pv_syntax (e.g. “{label} {id}”
• Interim: Do this as a command line option on vskit E.g. –pv-syntax “{label} {id}”