code: def sakoe_chiba_mask(sz1, sz2, radius=1, be=None):
      """Compute the Sakoe-Chiba mask.
  
      Parameters
      ----------
      sz1 : int
          The size of the first time series
      sz2 : int
          The size of the second time series.
      radius : int
          The radius of the band.
      be : Backend object or string or None
          Backend. If `be` is an instance of the class `NumPyBackend` or the string `"numpy"`,
          the NumPy backend is used.
          If `be` is an instance of the class `PyTorchBackend` or the string `"pytorch"`,
          the PyTorch backend is used.
          If `be` is `None`, the backend is determined by the input arrays.
          See our :ref:`dedicated user-guide page <backend>` for more information.
  
      Returns
      -------
      mask : array-like, shape=(sz1, sz2)
          Sakoe-Chiba mask.
  
      Examples
      --------
      >>> sakoe_chiba_mask(4, 4, 1)
      array([[ 0.,  0., inf, inf],
             [ 0.,  0.,  0., inf],
             [inf,  0.,  0.,  0.],
             [inf, inf,  0.,  0.]])
      >>> sakoe_chiba_mask(7, 3, 1)
      array([[ 0.,  0., inf],
             [ 0.,  0.,  0.],
             [ 0.,  0.,  0.],
             [ 0.,  0.,  0.],
             [ 0.,  0.,  0.],
             [ 0.,  0.,  0.],
             [inf,  0.,  0.]])
      """
      be = instantiate_backend(be)
      mask = be.full((sz1, sz2), be.inf)
      if sz1 > sz2:
          width = sz1 - sz2 + radius
          for i in range(sz2):
              lower = max(0, i - radius)
              upper = min(sz1, i + width) + 1
              mask[lower:upper, i] = 0.0
      else:
          width = sz2 - sz1 + radius
          for i in range(sz1):
              lower = max(0, i - radius)
              upper = min(sz2, i + width) + 1
              mask[i, lower:upper] = 0.0
      return mask
  
imports: import warnings
  import numpy
  from numba import njit, prange
  from tslearn.backend import instantiate_backend
  from tslearn.utils import to_time_series
  from .utils import _cdist_generic
label_desc: Use image node_id 27 for calling a global function with example usage: sakoe_chiba_mask(sz1, sz2, radius, be) and returns: mask