fix: remove duplicate 'Methods as Properties' section

Author: JustATrick

_guides/helpers.md

@@ -273,119 +273,6 @@ Assertion.addChainableMethod('age', assertModelAge, chainModelAge);
 
 Done. Now we can assert Arthur's exact age. We will pick up again with this example when learning how to overwrite methods.
 
-### Methods as Properties
-
-Chai includes a unique utility that allows you to construct a language chain that can function
-as either a property or a method. We call these "chainable methods". Despite the fact that we
-demonstrated the "is model of model" as both a property and a method, these assertions are NOT
-a good use case for chainable methods.
-
-##### When to Use
-
-To understand when to best use chainable methods we will examine a chainable method from Chai's
-core.
-
-```javascript
-var arr = [ 1, 2, 3 ]
-  , obj = { a: 1, b: 2 };
-
-expect(arr).to.contain(2);
-expect(obj).to.contain.key('a');
-```
-
-For this to work, two seperate functions are needed. One that will be invoked when the
-chain is used as either a property or a method, and one that will be invoked when only used
-as a method.
-
-In these examples, and with all of the other chainable methods in core, the only function
-of `contain` as a property is to set a `contains` flag to true. This indicates to `keys` to
-behave differently. In this case, when `key` is used in conjunction with `contain`, it will check
-for the inclusion of a key, instead of checking the exact match to all keys.
-
-##### When NOT to Use
-
-Let's say we set up a chainable method for `model` to behave as we indicated above: do an `instanceof`
-check if used as a property, and a `_type` check if used as a method. The following conflict would occur...
-
-The following would work...
-
-```javascript
-expect(arthur).to.be.a.model;
-expect(arthur).to.be.a.model('person');
-expect(arr).to.not.be.a.model;
-```
-
-But the following would not...
-
-```javascript
-expect(arthur).to.not.be.a.model('person');
-```
-
-Remember, since the function used as the property assertion is invoked when also used as a method,
-and negation impacts ALL assertions after it is set, we would receive an error message resembling
-`expected [object Model] not to be instance of [object Model]`. As such, please obey this general
-guideline when constructing chainable methods.
-
-> When constructing chainable methods, the property function should only serve to set a flag
-> for later modifying the behavior of an existing assertion.
-
-##### An Appropriate Example
-
-For use with our model example, we are going to construct an example that allows us to test Arthur's
-age exactly, or chain into Chai's numerical comparators, such as `above`, `below`, and `within`. You will
-need to learn how to overwrite methods without destroying core functionality, but we get to that a bit later.
-
-Our goal will allow for all of the following to pass.
-
-```javascript
-expect(arthur).to.have.age(27);
-expect(arthur).to.have.age.above(17);
-expect(arthur).to.not.have.age.below(18);
-```
-
-Let's start first by composing the two functions needed for a chainable method. First up is the function
-to use when invoking the `age` method.
-
-```javascript
-function assertModelAge (n) {
-  // make sure we are working with a model
-  new Assertion(this._obj).to.be.instanceof(Model);
-
-  // make sure we have an age and its a number
-  var age = this._obj.get('age');
-  new Assertion(age).to.be.a('number');
-
-  // do our comparison
-  this.assert(
-      age === n
-    , "expected #{this} to have have #{exp} but got #{act}"
-    , "expected #{this} to not have age #{act}"
-    , n
-    , age
-  );
-}
-```
-
-By now, that should be self-explanitory. Now for our property function.
-
-```javascript
-function chainModelAge () {
-  utils.flag(this, 'model.age', true);
-}
-```
-
-We will later teach our numerical comparators to look for that flag and change its behavior. Since we don't want to
-break the core methods, we will need to safely override that method, but we'll get to that in a minute. Let's
-finish up here first...
-
-```javascript
-Assertion.addChainableMethod('age', assertModelAge, chainModelAge);
-```
-
-<a href="/api/plugins/#addChainableMethod-section" class="clean-button">View addChainableMethod API</a>
-
-Done. Now we can assert Arthur's exact age. We will pick up again with this example when learning how to overwrite methods.
-
 ## Overwriting Language Chains
 
 Now that we can successfully add assertions to the language chain,