### Question:
Where extends Builder<T, P> { protected boolean isInvalidColumn(Term t) { if (t.isLeaf() || !t.getTerm(0).isLeaf()) return false; Collection collection = getParent().getCollection(); String function = t.getToken(); String column = t.getToken(0); if (function.equalsIgnoreCase("_key")) return false; if (column.indexOf(".") > 0 && collection != null) { String relName = Utils.substringBefore(column, "."); Relationship relationship = collection.getRelationship(relName); if (relationship != null) { collection = relationship.getRelated(); column = Utils.substringAfter(column, "."); } else { return false; } } return isInvalidColumn(collection, column); } Where(P query); List<Term> getFilters();  }### Answer:
@Test public void isInvalidColumn() { Where where = new Where(new Query()); assertFalse(where.isInvalidColumn(RqlParser.parse("function(column,1,2,3)"))); assertFalse(where.isInvalidColumn(RqlParser.parse("function(column_name,1,2,3)"))); assertTrue(where.isInvalidColumn(RqlParser.parse("function(_column,1,2,3)"))); assertTrue(where.isInvalidColumn(RqlParser.parse("function(col-umn,1,2,3)"))); }