docs: def get_pistacking_frequency(self,analysis_cutoff):
          """Calculates the frequency of pi-pi interactions throughout simulations. If the frequency exceeds the
          analysis cutoff, this interaction will be plotted in the final figure.
          Takes:
              * analysis_cutoff * - fraction of simulation time a feature has to be present for to be plotted
          Output:
              * self.pi_contacts_for_drawing * - dictionary of pi-pi interactions to be plotted """
          self.frequency = defaultdict(int)
          for traj in self.pistacking_by_type:
              for contact in self.pistacking_by_type[traj]:
                  self.frequency[contact["ligand_ring_ids"],contact["type"],contact["resid"],contact["resname"],contact["segid"]]+=contact["frequency"]
          draw_frequency = {i:self.frequency[i] for i in self.frequency if self.frequency[i]>(int(len(self.trajectory))*float(analysis_cutoff))}
  
          self.pi_contacts_for_drawing = {}
          for contact in draw_frequency:
              self.pi_contacts_for_drawing[contact]=draw_frequency[contact]