class_docstr: Try to figure out the batchsize, but never error out
  
  If this cannot figure out anything else, will fallback to guessing 1
  
  Example
  -------
  >>> guesser = BatchsizeGuesser()
  >>> # Works with simple tensors:
  >>> guesser(torch.randn((2,3)))
  2
  >>> # Works with sequences of tensors:
  >>> guesser((torch.randn((2,3)), torch.randint(high=5, size=(2,))))
  2
  >>> # Works with PaddedBatch:
  >>> guesser(PaddedBatch([{"wav": [1.,2.,3.]}, {"wav": [4.,5.,6.]}]))
  2
  >>> guesser("Even weird non-batches have a fallback")
  1
docstr: Implementation of len_of_first.
docstr_tok: ["Implementation","of","len_of_first","."]
code: def len_of_first(self, batch):
      """Implementation of len_of_first."""
      return len(batch[0])
  
imports: import collections
  import torch
  from speechbrain.utils.data_utils import mod_default_collate
  from speechbrain.utils.data_utils import recursive_to
  from speechbrain.utils.data_utils import batch_pad_right
  from torch.utils.data._utils.collate import default_convert
  from torch.utils.data._utils.pin_memory import pin_memory
label_desc: Use image node_id 6 for calling the BatchsizeGuesser obj's underlying member method code with example usage: obj.len_of_first(batch) and returns: len