# About

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The functions and classes in external libraries are diverse, but a majority can be configured using `pconfigs` tools. This section outlines design patterns in external libraries, and describes how to create config for them.

Note: with limited exceptions, the tools in this section should only be used to configure external libraries, as their design patterns are not always best practice for configurable systems. Good design patterns are discussed in [Design Patterns](../patterns/about).
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```{rubric} Subsections
:class: section-caption
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- [Functions](functions)
  - {ref}`subsec-configure-a-function`
  - {ref}`subsec-use-configured-functions`
- [Classes](classes)
  - {ref}`subsec-configure-an-external-class`
  - {ref}`subsec-extend-an-external-class`