def isTrue(val):
  """Determines if a textual value represents 'true'.

  Args:
    val: A string, which may be 'true', 'yes', 't', '1' to indicate True.
  Returns:
    True or False
  """
  val = val.lower()
  return val == 'true' or val == 't' or val == '1' or val == 'yes'