<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _replace_path(self, path):
 """ Get the replacement value for a path """

        if path in self._field_to_key:
            return self._field_to_key[path]
        next_key = "#f%d" % self._next_field
        self._next_field += 1
        self._field_to_key[path] = next_key
        self._fields[next_key] = path
        return next_key