code: def parse_split(cls, header: bytes, body: bytes) -> 'MessageContent':
          
          header_lines = cls._find_lines(header)
          body_lines = cls._find_lines(body)
          header_view = memoryview(header)
          body_view = memoryview(body)
          return cls._parse_split([header_view, body_view], header, body,
                                  header_view, body_view,
                                  header_lines, body_lines)
docs: Parse the header and body bytestrings into message content.
  
          Args:
              header: The header bytestring to parse.
              body: The body bytestring to parse.