How to use the schema.schema.Metafield function in schema

def _create_index_for_attribute(name_or_all, index_type, recreate=False):
    from schema.schema import Metafield

    creation_func = getattr(mediatumfunc, "create_attrindex_" + index_type)

    if name_or_all == "all":
        # find all search / sort metafields
        if index_type == "search":
            flags = "%s%"
        elif index_type == "sort":
            flags = "%o%"

        metafield_names = (t[0] for t in q(Metafield.name).filter(Metafield.a.opts.like(flags)).distinct())
        created_indices = []
        failed_indices = []

        for attrname in metafield_names:
            try:
                created = exec_sqlfunc(s, creation_func(attrname, recreate))
            except sqlalchemy.exc.OperationalError:
                logg.exception("failed to create %s index for %s", index_type, attrname)
                s.rollback()
                failed_indices.append(attrname)
            else:
                if created:
                    s.commit()
                    created_indices.append(attrname)

        logg.info("created %s indices for %s attributes, %s failed: %s",

field = Metafield("from")
        field.set("label", t(lang, "admin_wfstep_checkcontent_sender"))
        field.set("type", "text")
        ret.append(field)

        field = Metafield("email")
        field.set("label", t(lang, "admin_wfstep_checkcontent_recipient"))
        field.set("type", "text")
        ret.append(field)

        field = Metafield("subject")
        field.set("label", t(lang, "admin_wfstep_checkcontent_subject"))
        field.set("type", "text")
        ret.append(field)

        field = Metafield("text")
        field.set("label", t(lang, "admin_wfstep_checkcontent_text"))
        field.set("type", "memo")
        ret.append(field)

        return ret

def metaFields(self, lang=None):
        metafields = Container.metaFields(self, lang=lang)
        field = Metafield(u"style_hide_empty")

        field.set("label", t(lang, "hide empty directories"))
        field.set("type", u"check")
        metafields.append(field)
        return metafields

def metaFields(self, lang=None):
        ret = []
        field = Metafield("from")
        field.set("label", t(lang, "admin_wfstep_checkcontent_sender"))
        field.set("type", "text")
        ret.append(field)

        field = Metafield("email")
        field.set("label", t(lang, "admin_wfstep_checkcontent_recipient"))
        field.set("type", "text")
        ret.append(field)

        field = Metafield("subject")
        field.set("label", t(lang, "admin_wfstep_checkcontent_subject"))
        field.set("type", "text")
        ret.append(field)

        field = Metafield("text")
        field.set("label", t(lang, "admin_wfstep_checkcontent_text"))
        field.set("type", "memo")
        ret.append(field)

        return ret

def metaFields(self, lang=None):
        ret = list()
        field = Metafield("upload_pdfform")
        field.set("label", t(lang, "workflowstep-addformpage_label_upload_pdfform"))
        field.set("type", "upload")
        ret.append(field)

        field = Metafield("pdf_fields_editable")
        field.set("label", t(lang, "workflowstep-addformpage_label_pdf_fields_editable"))
        field.set("type", "check")
        ret.append(field)

        field = Metafield("pdf_form_separate")
        field.set("label", t(lang, "workflowstep-addformpage_label_pdf_form_separate"))
        field.set("type", "check")
        ret.append(field)

        field = Metafield("pdf_form_overwrite")
        field.set("label", t(lang, "workflowstep-addformpage_label_pdf_overwrite"))
        field.set("type", "check")
        ret.append(field)
        return ret

def metaFields(self, lang=None):
        ret = list()
        field = Metafield("publishsetpublishedversion")
        field.set("label", t(lang, "admin_wfstep_publishsetpublishedversion"))
        field.set("type", "check")
        ret.append(field)

        field = Metafield("publishsetupdatetime")
        field.set("label", t(lang, "admin_wfstep_publishsetupdatetime"))
        field.set("type", "check")
        ret.append(field)
        return ret

def metaFields(self, lang=None):
        ret = []
        field = Metafield("endtext")
        field.set("label", t(lang, "admin_wfstep_endtext"))
        field.set("type", "memo")
        ret.append(field)

        field = Metafield("endremove")
        field.set("label", t(lang, "admin_wfstep_endremove"))
        field.set("type", "check")
        ret.append(field)

        field = Metafield("endsetupdatetime")
        field.set("label", t(lang, "admin_wfstep_endsetupdatetime"))
        field.set("type", "check")
        ret.append(field)
        return ret

def metaFields(self, lang=None):
        metafields = []

        field = Metafield(u"nodename", attrs={
            "label": t(lang, "node name"),
            "type": u"text"
        })
        metafields.append(field)

        field = Metafield(u"style_full", attrs={
            "label": t(lang, "full view style"),
            "type": u"list",
            "valuelist": u"full_standard;full_text"
        })
        metafields.append(field)

        field = Metafield(u"style", attrs={
            "label": t(lang, "style"),
            "type": u"list",
            "valuelist": u"thumbnail;list;text",

def metaFields(self, lang=None):
        ret = []
        field = Metafield("endtext")
        field.set("label", t(lang, "admin_wfstep_endtext"))
        field.set("type", "memo")
        ret.append(field)

        field = Metafield("endremove")
        field.set("label", t(lang, "admin_wfstep_endremove"))
        field.set("type", "check")
        ret.append(field)

        field = Metafield("endsetupdatetime")
        field.set("label", t(lang, "admin_wfstep_endsetupdatetime"))
        field.set("type", "check")
        ret.append(field)
        return ret