class_docstr: A NumPy ndarray-like object abstracted as shape and dtype.
  
  Main use is for representing input and output signatures.
docstr: Returns length of 1; relevant to input and output signatures.
docstr_tok: ["Returns","length","of","1",";","relevant","to","input","and","output","signatures","."]
code: def __len__(self):
      """Returns length of 1; relevant to input and output signatures."""
      return 1
  
file_path: trax/trax/shapes.py
imports: import numpy
  import tensorflow
label_desc: Use image node_id 5 for calling the ShapeDtype obj's underlying member method code with example usage: obj.__len__() and returns: int