function pipelineColourspace (colourspace) {
  if (!is.string(colourspace)) {
    throw is.invalidParameterError('colourspace', 'string', colourspace);
  }
  this.options.colourspacePipeline = colourspace;
  return this;
}
Set the pipeline colourspace.

The input image will be converted to the provided colourspace at the start of the pipeline.
All operations will use this colourspace before converting to the output colourspace,
as defined by {@link #tocolourspace|toColourspace}.

@since 0.29.0

@example
// Run pipeline in 16 bits per channel RGB while converting final result to 8 bits per channel sRGB.
await sharp(input)
 .pipelineColourspace('rgb16')
 .toColourspace('srgb')
 .toFile('16bpc-pipeline-to-8bpc-output.png')

@param {string} [colourspace] - pipeline colourspace e.g. `rgb16`, `scrgb`, `lab`, `grey16` [...](https://github.com/libvips/libvips/blob/41cff4e9d0838498487a00623462204eb10ee5b8/libvips/iofuncs/enumtypes.c#L774)
@returns {Sharp}
@throws {Error} Invalid parameters