docs: def encode(self, boundary):
          """Returns the string encoding of this parameter"""
          if self.value is None:
              value = self.fileobj.read()
          else:
              value = self.value
  
          if re.search("^--%s$" % re.escape(boundary), value, re.M):
              raise ValueError("boundary found in encoded string")
  
          return "%s%s\r\n" % (self.encode_hdr(boundary), value)