Number type MultipleOf fields are not being parsed and are always null

The "multipleOf" fields for number types are not being parsed, they always seem to be null have attached a Scala unit test to replicate:

import io.swagger.v3.parser.OpenAPIV3Parser
import io.swagger.v3.parser.core.models.ParseOptions


class MultipleOfTest {

  "multiple of" should "be not null" in
  {
    val openApiDef =
      """openapi: 3.0.0
        |info:
        |  version: 0.0.0
        |  title: "test"
        |components:
        |  schemas:
        |    AssessCandidate:
        |      type: object
        |      properties:
        |        candidate:
        |          type: object
        |          properties:
        |            id:
        |              type: string
        |          required:
        |          - id
        |        test_results:
        |          type: object
        |          properties:
        |            id:
        |              type: string
        |            status:
        |              type: string
        |            score:
        |              type: number
        |              multipleOf: 1
        |            date:
        |              type: string
        |              format: date
        |            comment:
        |              type: string
        |            result_url:
        |              type: string
        |      required:
        |      - candidate
        |      - test_results
        |""".stripMargin
    
    val multipleOf = new OpenAPIV3Parser().readContents(openApiDef, null, new ParseOptions).getOpenAPI.getComponents.getSchemas.get("AssessCandidate").getProperties.get("score").getMultipleOf
    assert(multipleOf != null)
    }
  }

Start with the OpenAPIV3Parser.readContents entry point and the Scala unit test shown in the issue, using the supplied OpenAPI definition with a numeric multipleOf value. Confirm that the parsed score schema returns a non-null getMultipleOf value, and preserve coverage for this case in the parser tests.