Fixes indentation of solution of multiple preprocessors challenge

[sverhoeven]

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Closes {Link to the corresponding issue}

[sverhoeven]

Tested by running following recipe

recipe_example_multi_preprocessors.yml

# ESMValTool
# recipe_example.yml
---
documentation:
  description: Demonstrate basic ESMValTool example

  authors:
    - demora_lee
    - mueller_benjamin
    - swaminathan_ranjini

  maintainer:
    - demora_lee

  references:
    - demora2018gmd
    # Some plots also appear in ESMValTool paper 2.

  projects:
    - ukesm

datasets:
  - {dataset: UKESM1-0-LL, project: CMIP6, exp: historical,
     ensemble: r1i1p1f2} #single dataset as an example

preprocessors:
  prep_map:
    regrid:    #apply the preprocessor to regrid
      target_grid: 1x1 # target resolution
      scheme: linear  #how to interpolate for regridding

  prep_map_land:
    custom_order: true #ensure that given order of preprocessing is followed
    mask_landsea:    #apply a mask
      mask_out: sea   #mask out sea grid cells
    regrid:    # now apply the preprocessor to regrid
      target_grid: 1x1 # target resolution
      scheme: linear  #how to interpolate for regridding

diagnostics:
  # --------------------------------------------------
  # Two Simple diagnostics that illustrate the use of
  # different preprocessors
  # --------------------------------------------------
  diag_simple_plot:
    description: # preprocess a variable for a simple 2D plot
    variables:
      tas:  # surface temperature
        preprocessor: prep_map
        mip: Amon
        grid: gn #can change for variables from the same model
        start_year: 1970
        end_year: 2000
    scripts: null

  diag_land_only_plot:
    description: #preprocess a variable for a 2D land only plot
    variables:
      tas:  # surface temperature
        preprocessor: prep_map_land
        mip: Amon
        grid: gn #can change for variables from the same model
        start_year: 1970
        end_year: 2000
    scripts: null

[Peter9192]

Hey @sverhoeven ,
Very well spotted, I completely agree that the example should be correct. However, there are some other code snippets in the same file where the indentation also seems off (but that are not complete recipes). I think we should fix those as well. E.g.:

    variables:
        timeseries_variable:
        short_name: thetaoga
        preprocessor: prep_timeseries_1

[sverhoeven]

In your example the the yaml is still valid.
Fixing all solution of episode 5 is out of scope for this PR.

I would like store the solution recipes for checks in CI and to use the diff view in the Markdown files so I am sure the reader gets correct solution, see #110

[Peter9192]

In your example the the yaml is still valid.

It may be valid but it's good practice to stick to 2 indents, so it should be:

    variables:
      timeseries_variable:
        short_name: thetaoga
        preprocessor: prep_timeseries_1

Fixing all solution of episode 5 is out of scope for this PR.

Then let's open another issue for fixing these, because I do think we should.