@Override
	public T getAt(long snap, Address address) {
		T unit = getContaining(snap, address);
		if (unit == null) {
			return null;
		}
		if (!unit.getAddress().equals(address)) {
			return null;
		}
		return unit;
	}
Subtract from cur, the boxes covered by the entries intersecting the given query box

<p>
Compute C = A - B, where A B and C are sets of (possibly overlapping) boxes. A is given by
{@code} cur, and B is the set of bounding boxes for entries intersecting the query box. Two
temporary sets must be provided, and {@code cur} must be identical to one of them. This
routine will mutate them. The returned result will be identical to one of them.

<p>
If repeated subtraction is needed, the temporary sets need only be constructed once. For each
subsequent round of subtraction, {@code cur} should be the returned result of the previous
round. The final result is the return value of the final round.

<p>
This is used in the implementation of {@link #coversRange(TraceAddressSnapRange)}.

@param span the lifespan of the query box
@param range the address range of the query box
@param cur the set of boxes, identical to one of the temporary working sets.
@param set1 a temporary set for working
@param set2 a temporary set for working
@return the result of subtraction, identical to one of the temporary working sets
Ghidra/Debug/Framework-TraceModeling/src/main/java/ghidra/trace/database/listing/AbstractBaseDBTraceDefinedUnitsView.java