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private_instance_methods 

        # Module.private_instance_methods

(from ruby core)
---
    mod.private_instance_methods(include_super=true)    -> array

---

Returns a list of the private instance methods defined in *mod*. If the
optional parameter is `false`, the methods of any ancestors are not
included.

    module Mod
      def method1()  end
      private :method1
      def method2()  end
    end
    Mod.instance_methods           #=> [:method2]
    Mod.private_instance_methods   #=> [:method1]

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