composeAnd function
Implementation
String composeAnd(final And and) => and.expressions.map((Expression exp) {
final sb = new StringBuffer();
if (exp.length != 1) {
sb.write('(');
}
sb.write(composeExpression(exp));
if (exp.length != 1) {
sb.write(')');
}
return sb.toString();
}).join(' AND ');