[Discuss-gnuradio] Error in creating block

[Vishwanatha H G]

Hi..

 I crated a block named 'costas_loop_cc'. but when I connect to test this block with NULL sink and NULL Source, shows the error like this:
Error 1:
Generating: "/home/lekha/top_block.py"
Executing: "/home/lekha/top_block.py"

  File "/home/lekha/top_block.py", line 31
    self.costas_loop_cc_0 = -------->
                                    ^
SyntaxError: invalid syntax

>>> Done

the part of the generated  top_block.py code related to error is:
   ##################################################
        # Blocks
        ##################################################
        self.costas_loop_cc_0 = -------->line 31
        cannot find 'loop_bw': digital.costas_loop_cc($loop_bw, $order)
        <--------
        self.blocks_null_source_0 = blocks.null_source(gr.sizeof_gr_complex*1)
        self.blocks_null_sink_0 = blocks.null_sink(gr.sizeof_gr_complex*1)

        ##################################################
        # Connections
        ##################################################
        self.connect((self.blocks_null_source_0, 0), (self.costas_loop_cc_0, 0))
        self.connect((self.costas_loop_cc_0, 0), (self.blocks_null_sink_0, 0))

I wish it is a small error but I couldn’t  get. while creating a block when I execute  gr_modtool makexml command it shows the error :

AttributeError: 'NoneType' object has no attribute 'group'.

 what does it mean AttributeError? Is there any relation with this to above mentioned error. thanks for your advice