maximum (value, schema, opts) {
    // Must be a number
    const maximum = schema.maximum
    // Must be a boolean
    // Depends on maximum
    // default: false
    const exclusiveMaximum = schema.exclusiveMaximum
    if (typeof value === typeof maximum && !(exclusiveMaximum ? maximum > value : maximum >= value)) {
      return exclusiveMaximum
        ? makeError(value, `no more than nor equal to ${maximum}`, opts)
        : makeError(value, `no more than ${maximum}`, opts)
    }
  }
Validates the provided number against a maximum value defined by the Schema's `maximum` keyword
Validation succeeds if the value is a number, and is less than, or equal to, the value of this keyword.
http://json-schema.org/latest/json-schema-validation.html#anchor17

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