graph-builder/markdown/graph-builder.endpointpair.source.md

A graph builder library for modeling abstract graph structures.

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# EndpointPair.source method

If this [EndpointPair](./graph-builder.endpointpair.md) [EndpointPair.isOrdered](./graph-builder.endpointpair.isordered.md)<!-- -->, returns the node which is the source.

Throws an error if this [EndpointPair](./graph-builder.endpointpair.md) is not ordered.

**Signature:**
```javascript
abstract source(): N;
```
**Returns:** `N`