code: def write(self,new_filename,update_regul=True,version=None):
          
          if version is None:
              version = self._version
  
          if version == 1:
              return self._write_version1(new_filename=new_filename,update_regul=update_regul)
          elif version == 2:
              return self._write_version2(new_filename=new_filename, update_regul=update_regul)
          else:
              raise Exception("Pst.write() error: version must be 1 or 2, not '{0}'".format(version))
docs: main entry point to write a pest control file.
  
           Parameters
          ----------
          new_filename : str
              name of the new pest control file
          update_regul : (boolean)
              flag to update zero-order Tikhonov prior information
              equations to prefer the current parameter values
          version : int
              flag for which version of control file to write (must be 1 or 2).
              if None, uses Pst._version, which set in the constructor and modified
              during the load