code: def _compile(cls, lines):
          '''Return the filename from the current line.'''
          m = cls.RE_EXTEND.match(lines.current)
          if m is None:
              raise DefineBlockError('''Incorrect block definition at line {}, {}
  Should be something like: #extend path/foo.html:'''.format(
                  lines.pos, lines.current))
          return m.group(1f _compile(cls, lines):
          '''Return the filename from the current line.'''
          m = cls.RE_EXTEND.match(lines.current)
          if m is None:
              raise DefineBlockError('''Incorrect block definition at line {}, {}
  Should be something like: #extend path/foo.html:'''.format(
                  lines.pos, lines.current))
          return m.group(1)
docs: Return the filename from the current line.