human
Solve the following python programming problem given the following code:
def complete(self, line) : 
    '
        Returns an auto completed line and/or posibilities for completion.

        @param line: Given line so far.
        @type line: string

        @return: Line completed as for as possible,
        and possible further completions.
        @rtype: tuple
        ' 
    split_line = self._complete_sep.split (line) 
    possibilities = self._IP.complete (possibilities [(- 1)]) 
    if possibilities : 
        def _common_prefix(str1, str2) : 
            '
                Reduction function. returns common prefix of two given strings.

                @param str1: First string.
                @type str1: string
                @param str2: Second string
                @type str2: string

                @return: Common prefix to both strings.
                @rtype: string
                ' 
            for i in range (len (str1)) : 
                if (not str2.startswith (str1 [: (i + 1)])) : 
                    return str1 [: i] 
return str1 
common_prefix = reduce (_common_prefix, possibilities) 
        completed = (line [: (- len (split_line [(- 1)]))] + common_prefix) 
else : 
        completed = line 
return (completed, possibilities) 

    
    

    Fix the buggy line: possibilities = self._IP.complete (possibilities [(- 1)])
assistant
#Here is Python code to fix the buggy line: possibilities = self.

possibilities = self._IP.complete (split_line [(- 1)])