code: public T withStatement(Statement statement) {
  		PropertyIdValue pid = statement.getMainSnak()
  				.getPropertyId();
  		ArrayList<Statement> pidStatements = this.statements.get(pid);
  		if (pidStatements == null) {
  			pidStatements = new ArrayList<Statement>();
  			this.statements.put(pid, pidStatements);
  		}
  
  		pidStatements.add(statement);
  		return getThis();
  	}
docs: Adds an additional statement to the constructed document.
  
  @param statement
  the additional statement
  @return builder object to continue construction