human
Solve the following python programming problem given the following code:
def coalesce(* fields, **kwargs) : 
    '
    Return a function which accepts a row and returns the first non-missing
    value from the specified fields. Intended for use with
    :func:`petl.transform.basics.addfield`.

    ' 
    missing = kwargs.get ('missing', None) 
    default = kwargs.get ('default', None) 
    def _coalesce(row) : 
        for f in fields : 
            v = row [f] 
            if (v is not missing) : 
                return v 
return default 
return default 

    
    

    Fix the buggy line: return default
assistant
#Here is Python program to fix the buggy line: return default
.

return def _coalesce(