code: public T getValue(E row, E col) {
  		if(!rowKeys.containsKey(row))
  			return null;
  		if(!colKeys.containsKey(col))
  			return null;
  		try{
  			get(rowKeys.get(row)).get(colKeys.get(col));
  		} catch(IndexOutOfBoundsException e){
  			return null;
  		}
  		return get(rowKeys.get(row)).get(colKeys.get(col));
  	}
docs: Returns the matrix entry specified by the given row and col keys (Matrix[row,col]).
  @param row Row-value of indexing type
  @param col Col-value of indexing type
  @return Value at matrix position [row,col]