<p>
An interface type specifies a <a href="#Method_sets">method set</a> called its <i>interface</i>.
A variable of interface type can store a value of any type with a method set
that is any superset of the interface. Such a type is said to
<i>implement the interface</i>.
The value of an uninitialized variable of interface type is <code>nil</code>.
</p>

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