code: def batch_length(batch):
      '''Determine the number of samples in a batch.
  
      Parameters
      ----------
      batch : dict
          A batch dictionary.  Each value must implement `len`.
          All values must have the same `len`.
  
      Returns
      -------
      n : int >= 0 or None
          The number of samples in this batch.
          If the batch has no fields, n is None.
  
      Raises
      ------
      PescadorError
          If some two values have unequal length
      '''
      n = None
  
      for value in six.itervalues(batch):
          if n is None:
              n = len(value)
  
          elif len(value) != n:
              raise PescadorError('Unequal field lengths')
  
      return f batch_length(batch):
      '''Determine the number of samples in a batch.
  
      Parameters
      ----------
      batch : dict
          A batch dictionary.  Each value must implement `len`.
          All values must have the same `len`.
  
      Returns
      -------
      n : int >= 0 or None
          The number of samples in this batch.
          If the batch has no fields, n is None.
  
      Raises
      ------
      PescadorError
          If some two values have unequal length
      '''
      n = None
  
      for value in six.itervalues(batch):
          if n is None:
              n = len(value)
  
          elif len(value) != n:
              raise PescadorError('Unequal field lengths')
  
      return n
docs: Determine the number of samples in a batch.
  
      Parameters
      ----------
      batch : dict
          A batch dictionary.  Each value must implement `len`.
          All values must have the same `len`.
  
      Returns
      -------
      n : int >= 0 or None
          The number of samples in this batch.
          If the batch has no fields, n is None.
  
      Raises
      ------
      PescadorError
          If some two values have unequal length