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NotImplementedError 

        # NotImplementedError < ScriptError

(from ruby core)
---
Raised when a feature is not implemented on the current platform. For
example, methods depending on the `fsync` or `fork` system calls may
raise this exception if the underlying operating system or Ruby runtime
does not support them.

Note that if `fork` raises a `NotImplementedError`, then
`respond_to?(:fork)` returns `false`.
---

This is MURDOC! A Ruby documentation browser inspired by Smalltalk-80. It allows you to learn about Ruby by browsing through its class hierarchies, and see any of its methods.