anyOf (value, schema, opts) {
    let validated = false
    let allErrors = []
    schema.anyOf.forEach(function (_schema) {
      const errors = validate(value, _schema, opts)
      if (errors) {
        allErrors = allErrors.concat(errors)
      } else {
        validated = true
      }
    })
    return validated ? undefined : allErrors
  }
Validates the provided value against all schemas defined in the Schemas `anyOf` keyword.
The instance is valid against this keyword if and only if it is valid against
at least one of the schemas in this keyword's value.

The value of this keyword MUST be an array. This array MUST have at least one element.
Each element of this array MUST be an object, and each object MUST be a valid JSON Schema.
see http://json-schema.org/latest/json-schema-validation.html#anchor85

@name Schema.validationKeywords.anyOf
@method
@param {*} value Value to be validated.
@param {object} schema Schema containing the `anyOf` keyword.
@param {object} [opts] Configuration options.
@returns {(array|undefined)} Array of errors or `undefined` if valid.