code: def copy_file_internal(
      src_fs,  # type: FS
      src_path,  # type: Text
      dst_fs,  # type: FS
      dst_path,  # type: Text
  ):
      # type: (...) -> None
      
      if src_fs is dst_fs:
          # Same filesystem, so we can do a potentially optimized
          # copy
          src_fs.copy(src_path, dst_path, overwrite=True)
      elif dst_fs.hassyspath(dst_path):
          with dst_fs.openbin(dst_path, "w") as write_file:
              src_fs.download(src_path, write_file)
      else:
          with src_fs.openbin(src_path) as read_file:
              dst_fs.upload(dst_path, read_file)
docs: Low level copy, that doesn't call manage_fs or lock.
  
      If the destination exists, and is a file, it will be first truncated.
  
      This method exists to optimize copying in loops. In general you
      should prefer `copy_file`.
  
      Arguments:
          src_fs (FS): Source filesystem.
          src_path (str): Path to a file on the source filesystem.
          dst_fs (FS: Destination filesystem.
          dst_path (str): Path to a file on the destination filesystem.