docs: def writeTraj(filename='trajectory.input', data=[], ageunit=0, tunit=0,
                rhounit=0, idNum=0):
      '''
      Method for writeing Trajectory type ascii files files.
  
      Parameters
      ----------
      filename : string
          The file where this data will be written.
      data : list
          A list of 1D data vectors with time, T and rho.
      ageunit : integer, optional
          If 1 ageunit = SEC, If 0 ageunit = YRS. If 2 agunit =
          logtimerev in yrs.  The default is 0.  logtimerev is log of
          time until end
      tunit : integer, optional
          If 1 TUNIT  = T9K, if 0 TUNIT = T8K.  The default is 0.
      rhounit : integer, optional
          If 1 RHOUNIT = LOG, if 0 RHOUNIT = CGS. The default is 0.
      idNum : optional
          An optional id argument
  
      '''
      if data==[]:
          print('Please input correct data')
          print('returning None')
          return None
      headers=[]
      if ageunit ==1:
          headers.append('AGEUNIT = SEC')
      elif ageunit==0:
          headers.append('AGEUNIT = YRS')
      elif ageunit==2:
          headers.append('AGEUNIT = logtimerev/yrs')
  
      if tunit ==1:
          headers.append('TUNIT   = T9K')
      elif tunit==0:
          headers.append('TUNIT   = T8K')
  
      if rhounit ==1:
          headers.append('RHOUNIT = LOG')
      elif rhounit==0:
          headers.append('RHOUNIT = CGS')
  
      headers.append('ID = '+str(idNum))
  
      write(filename,headers,['time','T','rho'],data,['YRS/SEC; T8K/T9K; CGS/LOG',"FORMAT: '(10x,A3)'"],trajectory=True)