message: Fix docstring for strings.length
diff: @@ -13,7 +13,7 @@ END
  in_arg {
  name: "input"
  description: <<END
  -The string for which to compute the length.
  +The strings for which to compute the length for each element.
  END
  }
  out_arg {
  @@ -26,5 +26,12 @@ END
  summary: "String lengths of `input`."
  description: <<END
  Computes the length of each string given in the input tensor.
  +
  +>>> strings = tf.constant(['Hello','TensorFlow', '\U0001F642'])
  +>>> tf.strings.length(strings).numpy() # default counts bytes
  +array([ 5, 10, 4], dtype=int32)
  +>>> tf.strings.length(strings, unit="UTF8_CHAR").numpy()
  +array([ 5, 10, 1], dtype=int32)
  +
  END
  }
  