code: def _unsigned_subtract(a, b):
      """
      Subtract two values where a >= b, and produce an unsigned result
  
      This is needed when finding the difference between the upper and lower
      bound of an int16 histogram
      """
      # coerce to a single type
      signed_to_unsigned = {
          np.byte: np.ubyte,
          np.short: np.ushort,
          np.intc: np.uintc,
          np.int_: np.uint,
          np.longlong: np.ulonglong,
      }
      dt = np.result_type(a, b)
      try:
          unsigned_dt = signed_to_unsigned[dt.type]
      except KeyError:
          return np.subtract(a, b, dtype=dt)
      else:
          # we know the inputs are integers, and we are deliberately casting
          # signed to unsigned.  The input may be negative python integers so
          # ensure we pass in arrays with the initial dtype (related to NEP 50).
          return np.subtract(
              np.asarray(a, dtype=dt),
              np.asarray(b, dtype=dt),
              casting="unsafe",
              dtype=unsigned_dt,
          )
  
imports: import contextlib
  import functools
  import operator
  import warnings
  import numpy
  from numpy._core import overrides
label_desc: Use image node_id 12 for calling a global function with example usage: _unsigned_subtract(a, b) and returns: np, np