The raw card images are stored and parsed only if needed. The idea is that to create the HDU objects, only a small subset of standard cards is needed. Once a card is parsed, which is deferred to the Card class, the Card object is kept in a cache. This is useful because a small subset of cards is used a lot in the HDU creation process (NAXIS, XTENSION, ...).
This class provides a fast header parsing, without all the additional features of the Header class. Here only standard keywords are parsed, no support for CONTINUE, HIERARCH, COMMENT, HISTORY, or rvkc.
Hover to see nodes names; edges to Self not shown, Caped at 50 nodes.
Using a canvas is more power efficient and can get hundred of nodes ; but does not allow hyperlinks; , arrows or text (beyond on hover)
SVG is more flexible but power hungry; and does not scale well to 50 + nodes.
All aboves nodes referred to, (or are referred from) current nodes; Edges from Self to other have been omitted (or all nodes would be connected to the central node "self" which is not useful). Nodes are colored by the library they belong to, and scaled with the number of references pointing them
