code: def copy_file(
      src_fs,  # type: Union[FS, Text]
      src_path,  # type: Text
      dst_fs,  # type: Union[FS, Text]
      dst_path,  # type: Text
  ):
      # type: (...) -> None
      
      with manage_fs(src_fs, writeable=False) as _src_fs:
          with manage_fs(dst_fs, create=True) as _dst_fs:
              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)
              else:
                  # Standard copy
                  with _src_fs.lock(), _dst_fs.lock():
                      if _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: Copy a file from one filesystem to another.
  
      If the destination exists, and is a file, it will be first truncated.
  
      Arguments:
          src_fs (FS or str): Source filesystem (instance or URL).
          src_path (str): Path to a file on the source filesystem.
          dst_fs (FS or str): Destination filesystem (instance or URL).
          dst_path (str): Path to a file on the destination filesystem.