code: @NonNull
      public Expression from(@NonNull String alias) {
          if (alias == null) {
              throw new IllegalArgumentException("alias cannot be null.");
          }
          return new MetaExpression(this.keyPath, alias);
      }
docs: Specifies an alias name of the data source to query the data from.
  
  @param alias The data source alias name.
  @return The Meta expression with the given alias name specified.