>true</code> if and only if the argument is not <code>null</code>, is an <code>Expression</code>
 object that is the of the same type (<code>ValueExpression</code> or <code>MethodExpression</code>), and has an
 identical parsed representation.
 </p>

 <p>
 Note that two expressions can be equal if their expression Strings are different. For example,
 <code>${fn1:foo()}</code> and <code>${fn2:foo()}</code> are equal if their corresponding <code>FunctionMapper</code>s
 mapped <code>fn1:foo</code> and <code>fn