# $docid [ int ]
# Document for which to get a field.
# Default: current document

# $field [ string ]
# Field to get for the document:
# - any of the document object fields
#   (http://modxcms.com/the-document-object.html)
# - template variable assigned to the document
# Default: 'pagetitle'

# $parent [ 0 | 1 ]
# $parent = 1 - returns the field for the parent of the document.
# Default: 0

# $parentLevel [ int ]
# How high in the document tree to search for the parent of the document?
# - $parentLevel = 0 - returns the ultimate parent (right under site root)
# - $parentLevel = 1 - returns the direct parent
# Default: 0

# $topid [ int ]
# Id of the topmost document in the document tree under which to search for a
# parent.
# Default: 0