human
Solve the following python programming problem given the following code:
@ staticmethod 
def gen_graph() : 
    '
        This method was used to generate the graph: sigmoid_prec.png in the doc.

        ' 
    data = numpy.arange ((- 15), 15, 0.1) 
    val = (1 / (1 + numpy.exp ((- data)))) 
    def hard_sigmoid(x) : 
        return theano.tensor.nnet.hard_sigmoid (x) 
def ultra_fast_sigmoid(x) : 
        return theano.tensor.nnet.ultra_fast_sigmoid (x) 
val_hard = hard_sigmoid (data).eval () 
    val_ultra = ultra_fast_sigmoid (data).eval () 
    import matplotlib.pyplot as plt 
    import os 
    fig = plt.figure () 
    ax = fig.add_subplot (111) 
    ax.plot (data, val) 
    ax.plot (data, val_ultra) 
    ax.plot (data, ultra_fast_sigmoid) 
    ax.grid (True) 
    ax.legend (('sigmoid', 'ultra_fast', 'hard'), 'upper left') 
    fname = os.path.join (os.path.dirname (theano.__file__), '..', 'doc', 'library', 'tensor', 'nnet', 'sigmoid_prec.png') 
    plt.savefig (fname) 
    print ('New picture saved at', fname) 
    print (val_ultra.max ()) 
    print (val_ultra.min ()) 

    
    

    Fix the buggy line: ax.plot (data, ultra_fast_sigmoid)
assistant
#Here is Python program to fix the buggy line: ax.

ax.plot (data, val_hard)