code: public BooleanExpression startsWith(Expression<String> str) {
          return Expressions.booleanOperation(Ops.STARTS_WITH, mixin, str);
      }
docs: Create a {@code this.startsWith(str)} expression
  
  <p>Return true if this starts with str</p>
  
  @param str string
  @return this.startsWith(str)
  @see java.lang.String#startsWith(String)