human
Solve the following python programming problem given the following code:
def _swallow_next_tc(self, grid_width, top_tc) : 
    '
        Extend the horizontal span of this `w:tc` element to incorporate the
        following `w:tc` element in the row and then delete that following
        `w:tc` element. Any content in the following `w:tc` element is
        appended to the content of *top_tc*. The width of the following
        `w:tc` element is added to this one, if present. Raises
        |InvalidSpanError| if the width of the resulting cell is greater than
        *grid_width* or if there is no next `<w:tc>` element in the row.
        ' 
    def raise_on_invalid_swallow(next_tc) : 
        if (next_tc is None) : 
            raise InvalidSpanError ('not enough grid columns') 
if ((self.grid_span + next_tc.grid_span) > grid_width) : 
            raise InvalidSpanError ('span is not rectangular') 
next_tc = self._next_tc 
    raise_on_invalid_swallow (next_tc) 
    next_tc._move_content_to (top_tc) 
    self._add_width_of (next_tc) 
    self.grid_span += raise_on_invalid_swallow.grid_span 
    next_tc._remove () 

    
    

    Fix the buggy line: self.grid_span += raise_on_invalid_swallow.grid_span
assistant
#Here is Python code to fix the buggy line: self.

self.grid_span += next_tc.grid_span