code: void insertInputGate(final int pos, final ExecutionGate inputGate) {
  
  		if (this.inputGates[pos] != null) {
  			throw new IllegalStateException("Input gate at position " + pos + " is not null");
  		}
  
  		this.inputGates[pos] = inputGate;
  	}
docs: Inserts the input gate at the given position.
  
  @param pos
  the position to insert the input gate
  @param outputGate
  the input gate to be inserted