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/// @startDocuBlock collectionGeo
/// @brief constructs a geo index selection
/// `collection.geo(location-attribute)`
///
/// Looks up a geo index defined on attribute *location_attribute*.
///
/// Returns a geo index object if an index was found. The `near` or
/// `within` operators can then be used to execute a geo-spatial query on
/// this particular index.
///
/// This is useful for collections with multiple defined geo indexes.
///
/// `collection.geo(location_attribute, true)`
///
/// Looks up a geo index on a compound attribute *location_attribute*.
///
/// Returns a geo index object if an index was found. The `near` or
/// `within` operators can then be used to execute a geo-spatial query on
/// this particular index.
///
/// `collection.geo(latitude_attribute, longitude_attribute)`
///
/// Looks up a geo index defined on the two attributes *latitude_attribute*
/// and *longitude-attribute*.
///
/// Returns a geo index object if an index was found. The `near` or
/// `within` operators can then be used to execute a geo-spatial query on
/// this particular index.
///
/// Note: the *geo* simple query helper function is **deprecated** as of ArangoDB 
/// 2.6. The function may be removed in future versions of ArangoDB. The preferred
/// way for running geo queries is to use their AQL equivalents.
///
/// @EXAMPLES
///
/// Assume you have a location stored as list in the attribute *home*
/// and a destination stored in the attribute *work*. Then you can use the
/// `geo` operator to select which geo-spatial attributes (and thus which
/// index) to use in a `near` query.
///
/// @EXAMPLE_ARANGOSH_OUTPUT{geoIndexSimpleQuery}
/// ~db._create("complex")
/// |for (i = -90;  i <= 90;  i += 10) {
/// |  for (j = -180;  j <= 180;  j += 10) {
/// |    db.complex.save({ name : "Name/" + i + "/" + j,
/// |                      home : [ i, j ],
/// |                      work : [ -i, -j ] });
/// |  }
/// |}
///
///  db.complex.near(0, 170).limit(5); // xpError(ERROR_QUERY_GEO_INDEX_MISSING)
///  db.complex.ensureIndex({ type: "geo", fields: [ "home" ] });
///  db.complex.near(0, 170).limit(5).toArray();
///  db.complex.geo("work").near(0, 170).limit(5); // xpError(ERROR_QUERY_GEO_INDEX_MISSING)
///  db.complex.ensureIndex({ type: "geo", fields: [ "work" ] });
///  db.complex.geo("work").near(0, 170).limit(5).toArray();
/// ~ db._drop("complex");
/// @END_EXAMPLE_ARANGOSH_OUTPUT
/// 
///
/// @endDocuBlock
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