pe is an object, optional dictionary for
      well-defined properties, each given as: `property_name` : `property_data`

    * `additionalProperties`: if the type is an object, optional dictionary for
      properties with undefined names

    * `patternProperties`: if the type is an object, optional dictionary for
      properties with names adhering to a regex pattern

    * `items`: if the type is an array, array of dictionaries describing the
      format of the array's items

    * `anchor`: optional 