code: def _line_func_1(self, x):
      self.fcount += 1
      f = np.dot(x, x)
      df = 2 * x
      return f, df
  
imports: from numpy.testing import assert_, assert_equal, assert_array_almost_equal, assert_array_almost_equal_nulp, assert_warns, suppress_warnings
  import scipy.optimize.linesearch
  from scipy.optimize.linesearch import LineSearchWarning
  import numpy
label_desc: Use image node_id 4 for calling the TestLineSearch obj's underlying member method code with example usage: obj._line_func_1(x) and returns: f,  df