18.1.4.1 Objects
An object is a part that can be included within an element.
Most objects cannot contain objects.  Those which can will be specified.  Objects can only be found
in the following locations:
-  affiliated keywords defined in org-element-parsed-keywords,
-  document properties,
-  headline titles,
-  inlinetask titles,
-  item tags,
-  paragraphs,
-  table cells,
-  table rows, which can only contain table cell objects,
-  verse blocks.
-  Entities and LaTeX Fragments
-  Export Snippets
-  Footnote References
-  Inline Babel Calls and Source Blocks
-  Line Breaks
-  Links
-  Macros
-  Targets and Radio Targets
-  Statistics Cookies
-  Subscript and Superscript
-  Table Cells
-  Timestamps
-  Text Markup