old_contents: """A Fortran reaction network for integration into the StarKiller
  Microphysics set of reaction networks used by astrophysical hydrodynamics
  codes"""
  
  from __future__ import print_function
  
  import glob
  import os
  
  from pynucastro.networks import BaseFortranNetwork
  
  class StarKillerNetwork(BaseFortranNetwork):
      def __init__(self, *args, **kwargs):
          # Initialize BaseFortranNetwork parent class
          super(StarKillerNetwork, self).__init__(*args, **kwargs)
  
          # Set up some directories
          self.template_dir = os.path.join(self.pynucastro_dir,
                                           'templates',
                                           'starkiller-microphysics')
          self.template_file_select = os.path.join(self.template_dir,
                                                   '*.template')
          self.template_files = glob.glob(self.template_file_select)
  
      def _initial_mass_fractions(self, n_indent, of):
          # Redefine initial mass fractions tag to set the
          # mass fractions in the burn_cell unit test inputs file.
          for i, n in enumerate(self.unique_nuclei):
              of.write("\n# {nuc: <5} initial mass fraction\n".format(nuc=str(n)))
              of.write("{}massfractions({}) = 0.0d0\n".format(
                  self.indent*n_indent, i))
  
new_contents: """A Fortran reaction network for integration into the StarKiller
  Microphysics set of reaction networks used by astrophysical hydrodynamics
  codes"""
  
  from __future__ import print_function
  
  import glob
  import os
  
  from pynucastro.networks import BaseFortranNetwork
  
  class StarKillerNetwork(BaseFortranNetwork):
      def __init__(self, *args, **kwargs):
          # Initialize BaseFortranNetwork parent class
          super(StarKillerNetwork, self).__init__(*args, **kwargs)
  
          # Set up some directories
          self.template_dir = os.path.join(self.pynucastro_dir,
                                           'templates',
                                           'starkiller-microphysics')
          self.template_file_select = os.path.join(self.template_dir,
                                                   '*.template')
          self.template_files = glob.glob(self.template_file_select)
  
      def _initial_mass_fractions(self, n_indent, of):
          # Redefine initial mass fractions tag to set the
          # mass fractions in the burn_cell unit test inputs file.
          for i, n in enumerate(self.unique_nuclei):
              of.write("\n! {nuc: <5} initial mass fraction\n".format(nuc=str(n)))
              of.write("{}massfractions({}) = 0.0d0\n".format(
                  self.indent*n_indent, i))
  
subject: Use ! instead of # to comment Fortran :/