## Introspection API

 Stylus supports an introspection API. This allows mixins and functions to reflect relative to the caller, etc.


## mixin

  The `mixin` local variable is automatically assigned within function bodies.
  It contains the string `root` if the function was called at the root
  level, or `block` indicating otherwise, and finally `false` if the invoked function expects a return value.

  In the following example, we define `reset()` to alter its behaviour depending on whether it's mixed into root, into another block, or into a return value, as used in the `foo` property below:

      reset()
        if mixin == 'root'
          got
            root true
        else if mixin
          got 'a mixin'
        else
          'not a mixin'

      reset()

      body
        reset()
        foo reset()

Compiles to:

        got {
          root: true;
        }
        body {
          foo: "not a mixin";
          got: "a mixin";
        }