code: def run(self,exe_name="pestpp",cwd=None):
          
          filename = self.filename
          if self.new_filename is not None:
              filename = self.new_filename
          cmd_line = "{0} {1}".format(exe_name,os.path.split(filename)[-1])
          if cwd is None:
              cwd = os.path.join(*os.path.split(filename)[:-1])
              if cwd == '':
                  cwd = '.'
          print("executing {0} in dir {1}".format(cmd_line, cwd))
          pyemu.utils.os_utils.run(cmd_line,cwd=cwd)
docs: run a command related to the pst instance. If
          write() has been called, then the filename passed to write
          is in the command, otherwise the original constructor
          filename is used
  
          exe_name : str
              the name of the executable to call.  Default is "pestpp"
          cwd : str
              the directory to execute the command in.  If None,
              os.path.split(self.filename) is used to find
              cwd.  Default is None