Unable to dereference an schema 'alias'

[josh-burton]

This is a valid OpenApi schema setup, where a schema is essentially just an alias to a primitive type:

    "schemas": {
      "MyAlias": {
        "type": "string"
      },
      "MyObject": {
        "type": "object",
        "properties": {
          "myField": {
            "$ref": "#/components/schemas/MyAlias"
          }
        }
      }
    }

Currently the schema.deference method is unable to dereference MyAlias to the underlying schema type (string). Instead it returns the original object schema.