'Apply the import (rule) to the specified schema.
If the schema does not already contain an import for the
I{namespace} specified here, it is added.
@param root: A schema root.
@type root: L{Element}'

def apply(self, root):

    if (not self.filter.match(root, self.ns)):
        return
    if self.exists(root):
        return
    node = Element('import', ns=self.xsdns)
    node.set('namespace', self.ns)
    if (self.location is not None):
        node.set('schemaLocation', self.location)
    log.debug('inserting:    %s', node)
    root.insert(node)
