'Create a new :class:`.SchemeLink` from arguments and add it to
the scheme. The new link is returned.
Parameters
source_node : :class:`.SchemeNode`
Source node of the new link.
source_channel : :class:`.OutputSignal`
Source channel of the new node. The instance must be from
``source_node.output_channels()``
sink_node : :class:`.SchemeNode`
Sink node of the new link.
sink_channel : :class:`.InputSignal`
Sink channel of the new node. The instance must be from
``sink_node.input_channels()``
See also
.SchemeLink, Scheme.add_link'

def new_link(self, source_node, source_channel, sink_node, sink_channel):

    link = SchemeLink(source_node, source_channel, sink_node, sink_channel)
    self.add_link(link)
    return link
