code: def _atleast_2d_or_none(arg):
      if arg is not None:
          return atleast_2d(arg)
  
file_path: scipy/scipy/signal/_lti_conversion.py
imports: import numpy
  import numpy
  from numpy import r_, eye, atleast_2d, poly, dot, asarray, prod, zeros, array, outer
  from scipy import linalg
  from ._filter_design import tf2zpk, zpk2tf, normalize
label_desc: Use image node_id 3 for calling a global function with example usage: _atleast_2d_or_none(arg) and returns: atleast_2d