code: def slow_subm_int16(a, b):
      a = a.astype(np.int64)
      b = b.astype(np.int64)
      c = a - b
      return np.clip(c, -(2**15), 2**15 - 1).astype(np.int16)
  
imports: import mahotas
  import numpy
  from mahotas.morph import get_structuring_elem, subm, tophat_open, tophat_close
  import pytest
label_desc: Use image node_id 10 for calling a global function with example usage: slow_subm_int16(a, b) and returns: np