<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def old_collective_correlation( self ):
 """ Returns the collective correlation factor, f_I Args: None Returns: (Float):
 The collective correlation factor, f_I. Notes: This function assumes that the jump distance between sites has been normalised to a=1. If the jumps distance is not equal to 1 then the value returned by this function should be divided by a^2. Even better, use self.collective_correlation """

        if self.has_run:
            return self.atoms.collective_dr_squared() / float( self.number_of_jumps )
        else:
            return None