message: Change to use >>> and ... in docstring format, based on review comment
diff: @@ -123,29 +123,26 @@ def string_format(template, inputs, placeholder="{}", summarize=3, name=None):
  Example:
  Formatting a single-tensor template:
  ```python
  - tensor = tf.range(10)
  - formatted = tf.strings.format("tensor: {}, suffix", tensor)
  - expected = "tensor: [0 1 2 ... 7 8 9], suffix"
  -
  - assert(formatted == expected)
  + >>> tensor = tf.range(10)
  + >>> formatted = tf.strings.format("tensor: {}, suffix", tensor)
  + >>> expected = "tensor: [0 1 2 ... 7 8 9], suffix"
  + >>> assert(formatted == expected)
  ```
  Formatting a multi-tensor template:
  ```python
  - tensor_one = tf.reshape(tf.range(100), [10, 10])
  - tensor_two = tf.range(10)
  - formatted = tf.strings.format("first: {}, second: {}, suffix",
  - (tensor_one, tensor_two))
  -
  - expected = ("first: [[0 1 2 ... 7 8 9]\n"
  - " [10 11 12 ... 17 18 19]\n"
  - " [20 21 22 ... 27 28 29]\n"
  - " ...\n"
  - " [70 71 72 ... 77 78 79]\n"
  - " [80 81 82 ... 87 88 89]\n"
  - " [90 91 92 ... 97 98 99]], second: [0 1 2 ... 7 8 9], suffix")
  -
  - assert(formatted == expected)
  + >>> tensor_one = tf.reshape(tf.range(100), [10, 10])
  + >>> tensor_two = tf.range(10)
  + >>> formatted = tf.strings.format("first: {}, second: {}, suffix",
  + ... (tensor_one, tensor_two))
  + >>> expected = ("first: [[0 1 2 ... 7 8 9]\n"
  + ... " [10 11 12 ... 17 18 19]\n"
  + ... " [20 21 22 ... 27 28 29]\n"
  + ... " ...\n"
  + ... " [70 71 72 ... 77 78 79]\n"
  + ... " [80 81 82 ... 87 88 89]\n"
  + ... " [90 91 92 ... 97 98 99]], second: [0 1 2 ... 7 8 9], suffix")
  + >>> assert(formatted == expected)
  ```
  Args:
  