<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def display_line(self):
 """A single line describing this image"""

        msg = ["Image {0}".format(self.name)]
        if self.image_index:
            msg.append("Pushes to {0}".format(self.image_name))
        return ' : '.join(msg)