e.g. ["Revenues", "NetIncomeLoss"]. Leave empty to use the standard default set (revenue, net income, assets, liabilities, equity, EPS, cash). Raw values are always returned for any concept SEC reports. Period-over-period change (financial_changes) for a custom concept is only computed when it's a recognized balance-sheet-type (point-in-time) concept OR a normal duration concept with real period dates attached. A concept with SOME usable data but nothing comparable (e.g. only one period ever reported, or its latest period is currently ambiguous in SEC's own data) is reported under financial_changes.diffs[concept].incomplete_series with a stated reason — concepts_with_insufficient_history is reserved for a concept with no usable observations at all.