code: def define_residues_for_plotting_traj(self, analysis_cutoff):
          self.residue_counts_fraction = {}
          for traj in self.residue_counts:
              self.residue_counts_fraction[traj] = {residue:float(values)/len(self.contacts_per_timeframe[traj]) for residue,values in self.residue_counts[traj].items()}
          for traj in self.residue_counts_fraction:
              for residue in self.residue_counts_fraction[traj]:
                  self.frequency[residue].append(self.residue_counts_fraction[traj][residue])
          self.topology_data.dict_of_plotted_res = {i:self.frequency[i] for i in self.frequency if sum(self.frequency[i])>(int(len(self.trajectory))*analysis_cutoff)}
          assert len(self.topology_data.dict_of_plotted_res)!=0,"Nothing to draw for this ligand:(residue number: "+ str(self.topology_data.universe.ligand.resids[0]) +" on the chain "+ str(self.topology_data.universe.ligand.segids[0]) +") - try reducing the analysis cutoff."