code: public StringExpression trim() {
          if (trim == null) {
              trim = Expressions.stringOperation(Ops.TRIM, mixin);
          }
          return trim;
      }
docs: Create a {@code this.trim()} expression
  
  <p>Create a copy of the string, with leading and trailing whitespace
  omitted.</p>
  
  @return this.trim()
  @see java.lang.String#trim()