code: def ciphertext_length(header, plaintext_length):
      
      ciphertext_length = header_length(header)
      ciphertext_length += body_length(header, plaintext_length)
      ciphertext_length += footer_length(header)
      return ciphertext_length
docs: Calculates the complete ciphertext message length, given a complete header.
  
      :param header: Complete message header object
      :type header: aws_encryption_sdk.structures.MessageHeader
      :param int plaintext_length: Length of plaintext in bytes
      :rtype: int