code: def _fix0(aff):
      """Fix possible 0 time scaling from 0 TR
  
      Look in matrix part of affine (3, 3) in a (4, 4) affine).  If there is
      exactly one row and exactly one column in this part of the affine that are
      all exactly zero, assume this is a 0 scaling from a 0 TR in the header, and
      fix corresponding row, column index to 1.
  
      Parameters
      ----------
      aff : (M, N) array-like
          affine
  
      Returns
      -------
      fixed_aff : (M, N) affine
          which will be `aff` if no fix, and a new affine if fixed, with a 1
          instead of the zero in the offending row and column
  
      Examples
      --------
      >>> _fix0(np.diag([1, 2, 3, 0]))
      array([[1, 0, 0, 0],
             [0, 2, 0, 0],
             [0, 0, 3, 0],
             [0, 0, 0, 0]])
      >>> _fix0(np.diag([1, 0, 3, 0]))
      array([[1, 0, 0, 0],
             [0, 1, 0, 0],
             [0, 0, 3, 0],
             [0, 0, 0, 0]])
      """
      aff = np.asarray(aff)
      zeros = aff[:-1, :-1] == 0
      zrs = np.where(np.all(zeros, axis=1))[0]
      zcs = np.where(np.all(zeros, axis=0))[0]
      if len(zrs) != 1 or len(zcs) != 1:
          return aff
      fixed_aff = aff.copy()
      fixed_aff[zrs[0], zcs[0]] = 1
      return fixed_aff
  
imports: import warnings
  import numpy
  import numpy.linalg
  from nibabel import io_orientation
  from nibabel.affines import from_matvec, to_matvec
  from .coordinate_system import CoordinateSystem, is_coordsys, safe_dtype
  from .coordinate_system import product
label_desc: Use image node_id 16 for calling a global function with example usage: _fix0(aff) and returns: fixed_aff, aff