docs: def read_er_ages_file(self, path, ignore_lines_n, sort_by_these_names):
          '''
          read er_ages, sort it by site or sample (the header that is not empty)
          and convert ages to calendar year
  
          '''
          DATA = {}
          fin = open(path, 'r')
          # ignore first lines
          for i in range(ignore_lines_n):
              fin.readline()
          # header
          line = fin.readline()
          header = line.strip('\n').split('\t')
          # print header
          for line in fin.readlines():
              if line[0] == "#":
                  continue
              tmp_data = {}
              tmp_line = line.strip('\n').split('\t')
              for i in range(len(tmp_line)):
                  if i >= len(header):
                      continue
                  tmp_data[header[i]] = tmp_line[i]
              for name in sort_by_these_names:
                  if name in list(tmp_data.keys()) and tmp_data[name] != "":
                      er_ages_rec = self.convert_ages_to_calendar_year(tmp_data)
                      DATA[tmp_data[name]] = er_ages_rec
          fin.close()
          return(DATA)