docs: def _readPPN(self, fname, sldir):
          '''
          Private method that reads in and organizes the .ppn file
          Loads the data of the .ppn file into the variable cols.
  
          '''
          if sldir.endswith(os.sep):
                      #Making sure fname will be formatted correctly
              fname = str(sldir)+str(fname)
          else:
              fname = str(sldir)+os.sep+str(fname)
              self.sldir+=os.sep
          f=open(fname,'r')
          lines=f.readlines()
          for i in range(len(lines)):
              lines[i]=lines[i].strip()
  
          cols = ['ISOTP', 'ABUNDANCE_MF'] #These are constant, .ppn files have no header to read from
          for i in range(len(lines)):
              if not lines[i].startswith('H'):
                  index = i-1
                  break
  
          return cols, index