ropertyWriter">PropertyWriter</a>
for vertices or edges is a functor which can be called with two parameters:
<tt>std::ostream</tt> and either a vertex or an edge descriptor. It should output a
pair of brackets with a series of assigments &quot;name=value&quot; inside.
Each assignment should be separated either with space, with comma, or with semicolon.
The following functor, provided by BGL, is the example of PropertyWriter for
vertices or edges.  It is used to print the label of each vertex or edge.
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