Creating PFGSelectionStringField
================================
    >>> from Products.PFGSelectionStringField.content import PFGSelectionStringField
    >>> field = PFGSelectionStringField('field')
    >>> field
     <PFGSelectionStringField at field>
    >>> field.portal_type
    'PFGSelectionStringField'

    >>> from Products.PFGSelectionStringField.interfaces import IPFGSelectionStringField
    >>> IPFGSelectionStringField.providedBy(field)
    True

    >>> field.schema
    <Products.Archetypes.Schema.Schema object at ...>

    >>> field._at_rename_after_creation
    True

    >>> names = [field.getName() for field in field.schema.getSchemataFields('default')]
    >>> names
    ['id', 'title', 'description', 'required', 'hidden', 'fgDefault', 'fgVocabulary', 'fgFormat', 'subject', 'relatedItems', 'location', 'language', 'effectiveDate', 'expirationDate', 'creation_date', 'modification_date', 'creators', 'contributors', 'rights', 'allowDiscussion', 'excludeFromNav']

