Create placeholder name for the graph editor.
tf.contrib.graph_editor.placeholder_name( t=None, scope=None, prefix=_DEFAULT_PLACEHOLDER_PREFIX )
t: optional tensor on which the placeholder operation's name will be based on
scope: absolute scope with which to prefix the placeholder's name. None means that the scope of t is preserved. "" means the root scope.
prefix: placeholder name prefix.
A new placeholder name prefixed by "geph". Note that "geph" stands for Graph Editor PlaceHolder. This convention allows to quickly identify the placeholder generated by the Graph Editor.
TypeError: if t is not None or a tf.Tensor.