code: def _parse_section_three(self, part, mimetypes):
          
  
          link = 'tools.ietf.org/html/rfc2388#section-3'
  
          if part.disposition != 'form-data' or not part.name:
              self.fail('Each part of a multipart/form-data requires a '
                        'Content-Disposition header with a disposition type '
                        'of "form-data" AND a unique "name" parameter.', link)
          elif part.type.lower() not in mimetypes:
              allowed = ', '.join(mimetypes)
              self.fail('Invalid upload Content-Type. Each part of the '
                        'multipart/form-data upload MUST be one of: %s. '
                        '%s is not allowed.' % (allowed, part.type), link)
docs: Parse & validate a part according to section #3
  
          The logic applied follows section 3 guidelines from top
          to bottom.