////////////////////////////////////////////////////////////////////////////////
/// @startDocuBlock edgeCollectionEdges
/// @brief selects all edges for a set of vertices
/// `edge-collection.edges(vertex)`
///
/// The *edges* operator finds all edges starting from (outbound) or ending
/// in (inbound) *vertex*.
///
/// `edge-collection.edges(vertices)`
///
/// The *edges* operator finds all edges starting from (outbound) or ending
/// in (inbound) a document from *vertices*, which must a list of documents
/// or document handles.
///
/// @EXAMPLE_ARANGOSH_OUTPUT{EDGCOL_02_Relation}
///   db._create("vertex");
///   db._createEdgeCollection("relation");
/// ~ var myGraph = {};
///   myGraph.v1 = db.vertex.insert({ name : "vertex 1" });
///   myGraph.v2 = db.vertex.insert({ name : "vertex 2" });
/// | myGraph.e1 = db.relation.insert(myGraph.v1, myGraph.v2,
///                                   { label : "knows"});
///   db._document(myGraph.e1);
///   db.relation.edges(myGraph.e1._id);
/// ~ db._drop("relation");
/// ~ db._drop("vertex");
/// @END_EXAMPLE_ARANGOSH_OUTPUT
///
/// @endDocuBlock
////////////////////////////////////////////////////////////////////////////////