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/// @startDocuBlock API_EDGE_READ
/// @brief reads a single edge
///
/// @RESTHEADER{GET /_api/edge/{document-handle}, Read edge}
///
/// @RESTURLPARAMETERS
///
/// @RESTURLPARAM{document-handle,string,required}
/// The handle of the edge document.
///
/// @RESTHEADERPARAMETERS
///
/// @RESTHEADERPARAM{If-None-Match,string,optional}
/// If the "If-None-Match" header is given, then it must contain exactly one
/// etag. The edge is returned if it has a different revision than the
/// given etag. Otherwise an *HTTP 304* is returned.
///
/// @RESTHEADERPARAM{If-Match,string,optional}
/// If the "If-Match" header is given, then it must contain exactly one
/// etag. The edge is returned if it has the same revision ad the
/// given etag. Otherwise a *HTTP 412* is returned. As an alternative
/// you can supply the etag in an attribute *rev* in the URL.
///
/// @RESTDESCRIPTION
/// Returns the edge identified by *document-handle*. The returned
/// edge contains a few special attributes:
///
/// - *_id* contains the document handle
///
/// - *_rev* contains the revision
///
/// - *_from* and *to* contain the document handles of the connected
///   vertex documents
///
/// @RESTRETURNCODES
///
/// @RESTRETURNCODE{200}
/// is returned if the edge was found
///
/// @RESTRETURNCODE{304}
/// is returned if the "If-None-Match" header is given and the edge has
/// the same version
///
/// @RESTRETURNCODE{404}
/// is returned if the edge or collection was not found
///
/// @RESTRETURNCODE{412}
/// is returned if a "If-Match" header or *rev* is given and the found
/// document has a different version. The response will also contain the found
/// document's current revision in the *_rev* attribute. Additionally, the
/// attributes *_id* and *_key* will be returned.
/// @endDocuBlock
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