public String getCallString(int index) {
		return blockIndexToCallString.get(index);
	}
Returns the "call string" of a basic block, which represents the number and ordering
of CALL and CALLIND pcode ops with the block.
@param index block index
@return call string
Ghidra/Features/BSimFeatureVisualizer/src/main/java/ghidra/bsfv/BsfvTableModel.java