message: Remove _default_values_start_index in FunctionSpec - not needed.
diff: @@ -985,12 +985,11 @@ class FunctionSpec(object):
  self.vararg_name = fullargspec.varargs
  # A cache mapping from arg index to default value, for canonicalization.
  - offset = len(args) - len(fullargspec.defaults or [])
  + offset = len(args) - len(self._default_values or [])
  self._arg_indices_to_default_values = {
  offset + index: default
  - for index, default in enumerate(fullargspec.defaults or [])
  + for index, default in enumerate(self._default_values or [])
  }
  - self._default_values_start_index = offset
  if input_signature is None:
  self._input_signature = None
  else:
  @@ -1072,11 +1071,10 @@ class FunctionSpec(object):
  args = self._args_to_prepend + args
  kwargs = dict(kwargs, **self._kwargs_to_include)
  if not kwargs:
  - if self._default_values:
  - inputs = args + self._default_values[
  - len(args) - self._default_values_start_index:]
  - else:
  inputs = args
  + for index in sorted(self._arg_indices_to_default_values.keys()):
  + if index >= len(args):
  + inputs += (self._arg_indices_to_default_values[index],)
  else:
  # Maps from index of arg to its corresponding value, according to `args`
  # and `kwargs`; seeded with the default values for the named args that
  