Returns the number of bytes needed to serialize a non-repeated element.
  The returned byte count includes space for tag information and any
  other additional space associated with serializing value.

  Args:
    value: Value we're serializing.
    field_number: Field number of this value.  (Since the field number
      is stored as part of a varint-encoded tag, this has an impact
      on the total bytes required to serialize the value).
    field_type: The type of the field.  One of the TYPE_* constants
      within FieldDescriptor.

def _BytesForNonRepeatedElement(value, field_number, field_type):
  """Returns the number of bytes needed to serialize a non-repeated element.
  The returned byte count includes space for tag information and any
  other additional space associated with serializing value.

  Args:
    value: Value we're serializing.
    field_number: Field number of this value.  (Since the field number
      is stored as part of a varint-encoded tag, this has an impact
      on the total bytes required to serialize the value).
    field_type: The type of the field.  One of the TYPE_* constants
      within FieldDescriptor.
  """
  try:
    fn = type_checkers.TYPE_TO_BYTE_SIZE_FN[field_type]
    return fn(field_number, value)
  except KeyError:
    raise message_mod.EncodeError('Unrecognized field type: %d' % field_type)