def p_Body(p):
    '''
    Body : Line
         | Body Line
    '''
    if not isinstance(p[1], Body):
        p[0] = Body(None, p[1])
    else:
        p[0] = Body(p[1], p[2])
def p_Body ( p ) : if not isinstance ( p [ 1 ] , Body ) : p [ 0 ] = Body ( None , p [ 1 ] ) else : p [ 0 ] = Body ( p [ 1 ] , p [ 2 ] )
Body : Line
         | Body Line