Type-hint rename_schema.py

[LWprogramming]

Step 1 as outlined in PR 834

[obi1kenobi]

One minor typing nit, otherwise looks great!

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@c38b661). Click here to learn what that means.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##             master     #847   +/-   ##
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  Coverage          ?   94.76%           
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  Files             ?      108           
  Lines             ?     8398           
  Branches          ?        0           
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  Hits              ?     7958           
  Misses            ?      440           
  Partials          ?        0           

Impacted Files	Coverage Δ
...ql_compiler/schema_transformation/rename_schema.py	100.00% <100.00%> (ø)
graphql_compiler/compiler/helpers.py	93.63% <0.00%> (ø)
..._compiler/schema_generation/sqlalchemy/__init__.py	66.66% <0.00%> (ø)
...r/compiler/workarounds/orientdb_eval_scheduling.py	61.90% <0.00%> (ø)
...ql_compiler/compiler/ir_lowering_match/__init__.py	100.00% <0.00%> (ø)
graphql_compiler/compiler/context_helpers.py	100.00% <0.00%> (ø)
graphql_compiler/macros/macro_edge/descriptor.py	100.00% <0.00%> (ø)
...raphql_compiler/query_formatting/sql_formatting.py	100.00% <0.00%> (ø)
graphql_compiler/api/sql/mssql.py	0.00% <0.00%> (ø)
graphql_compiler/macros/macro_expansion.py	93.44% <0.00%> (ø)
... and 99 more

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[obi1kenobi]

Do we specifically need this to be a class attribute here? If not, can we move it to module-level and make it sit right adjacent to the Union definition that it duplicates?

[LWprogramming]

It's specifically used for RenameSchemaTypesVisitor, as it explicitly leaves out renaming the schema query type (i.e. SchemaQuery). RenameQueryTypeFieldsVisitor is the visitor that modifies the schema query type. Moving this class attribute to module-level could be confusing considering that we do actually modify the schema query type, just not in this particular class.