code: public static RAExpressionAttributes alias(RAExpressionAttributes re, RelationID alias) {
  
          ImmutableMap<QuotedID, Term> unqualifiedAttributes =
                  re.attributes.entrySet().stream()
                          .filter(e -> e.getKey().getRelation() == null)
                          .collect(ImmutableCollectors.toMap(
                                  e -> e.getKey().getAttribute(), Map.Entry::getValue));
  
          return create(unqualifiedAttributes, alias);
      }
docs: (relational expression) AS A
  
  @param re a {@link RAExpressionAttributes}
  @param alias a {@link QuotedID}
  @return a {@link RAExpressionAttributes}