human
Solve the following python programming problem given the following code:
@ derived_from (pd.DataFrame) 
def mean(self, axis = None, skipna = True) : 
    axis = self._validate_axis (skipna) 
    if (axis == 1) : 
        f = (lambda x : x.mean (axis = 1, skipna = skipna)) 
        name = '{0}mean(axis=1)'.format (self._token_prefix) 
        return map_partitions (f, None, self, token = name) 
else : 
        num = self._get_numeric_data () 
        s = num.sum (skipna = skipna) 
        n = num.count () 
        def f(s, n) : 
            try : 
                return (s / n) 
except ZeroDivisionError : 
                return np.nan 
name = '{0}mean-{1}'.format (self._token_prefix, tokenize (s)) 
        return map_partitions (f, None, s, n, token = name) 

    
    

    Fix the buggy line: axis = self._validate_axis (skipna)
assistant
#Here is Python code to fix the buggy line: axis = self.

axis = self._validate_axis (axis)