code: def slice2len(slicer, in_len):
      """Output length after slicing original length `in_len` with `slicer`
      Parameters
      ----------
      slicer : slice object
      in_len : int
  
      Returns
      -------
      out_len : int
          Length after slicing
  
      Notes
      -----
      Returns same as ``len(np.arange(in_len)[slicer])``
      """
      if slicer == slice(None):
          return in_len
      full_slicer = fill_slicer(slicer, in_len)
      return _full_slicer_len(full_slicer)
  
imports: import operator
  from functools import reduce
  from mmap import mmap
  from numbers import Integral
  import numpy
label_desc: Use image node_id 4 for calling a global function with example usage: slice2len(slicer, in_len) and returns: _full_slicer_len, in_len