code: private boolean containsValue(StatementGroup statementGroup, Value value) {
  		for (Statement s : statementGroup) {
  			if (value.equals(s.getValue())) {
  				return true;
  			}
  		}
  
  		return false;
  	}
docs: Checks if the given group of statements contains the given value as the
  value of a main snak of some statement.
  
  @param statementGroup
  the statement group to scan
  @param value
  the value to scan for
  @return true if value was found