def METHOD_NAME(self, separation):
    """Change the distance between a port and its anchor particle.
    separation : float, required
        Distance to shift port along the orientation vector from the anchor
        particle position. If no anchor is provided, the port will be
        shifted from the origin.
    """
    if self.used:
        warn(
            "This port is already being used and changing its separation "
            "will have no effect on the distance between particles."
        )
    if self.anchor:
        self.translate_to(self.anchor.pos)
    else:
        self.translate_to((0, 0, 0))
    self.translate(separation * self.direction)