docstr: Test if an empty array is returned if no peaks are provided.
docstr_tok: ["Test","if","an","empty","array","is","returned","if","no","peaks","are","provided","."]
code: def test_empty(self, x, xp, scp):
      """
      Test if an empty array is returned if no peaks are provided.
      """
      out = scp.signal.peak_prominences(x, [])
      return out
  
imports: import pytest
  import cupy
  from cupy.cuda import driver
  from cupy.cuda import runtime
  from cupy import testing
  import cupyx.scipy.signal
  import numpy
label_desc: Use image node_id 1 for calling the TestPeakProminences obj's underlying member method code with example usage: obj.test_empty(x, xp, scp) and returns: out