Context.as_template_fields() returns formatted Version.code field?

My templates.yml keys:

sg_version_code:
    type: str
    shotgun_entity_type: Version
    shotgun_field_name: code

if my context is a Version Context and I use

context.as_template_fields()

it returns the Version Code like this:

TST_0010_environ_0020-v045

However my version code is actually:

TST_0010_environ_0020.v045

Is there any filtering happening somewhere that could cause my dotted version to be reformatted to a hyphen?