Contributing to mvlearn

(adopted from scikit-learn)

Submitting a bug report or a feature request

We use GitHub issues to track all bugs and feature requests; feel free to open an issue if you have found a bug or wish to see a feature implemented.

In case you experience issues using this package, do not hesitate to submit a ticket to the Bug Tracker. You are also welcome to post feature requests or pull requests.

It is recommended to check that your issue complies with the following rules before submitting:

How to make a good bug report

When you submit an issue to Github, please do your best to follow these guidelines! This will make it a lot easier to provide you with good feedback:

  • The ideal bug report contains a short reproducible code snippet, this way anyone can try to reproduce the bug easily (see this for more details). If your snippet is longer than around 50 lines, please link to a gist or a github repo.

  • If not feasible to include a reproducible snippet, please be specific about what estimators and/or functions are involved and the shape of the data.

  • If an exception is raised, please provide the full traceback.

  • Please include your operating system type and version number, as well as your Python and mvlearn versions. This information can be found by running the following code snippet in Python.

    import platform; print(platform.platform());
    import sys; print("Python", sys.version);
    import mvlearn; print("mvlearn", mvlearn.version)
  • Please ensure all code snippets and error messages are formatted in appropriate code blocks. See Creating and highlighting code blocks for more details.

Contributing Code

The preferred workflow for contributing to mvlearn is to fork the main repository on GitHub, clone, and develop on a branch. Steps:

  1. Fork the project repository by clicking on the ‘Fork’ button near the top right of the page. This creates a copy of the code under your GitHub user account. For more details on how to fork a repository see this guide.

  2. Clone your fork of the mvlearn repo from your GitHub account to your local disk:

    $ git clone
    $ cd mvlearn
  3. Create a feature branch to hold your development changes:

    $ git checkout -b my-feature

    Always use a feature branch. It’s good practice to never work on the master branch!

  4. Develop the feature on your feature branch. Add changed files using git add and then git commit files:

    $ git add modified_files
    $ git commit

    to record your changes in Git, then push the changes to your GitHub account with:

    $ git push -u origin my-feature

Pull Request Checklist

We recommended that your contribution complies with the following rules before you submit a pull request:

  • Follow the coding-guidelines.

  • Give your pull request a helpful title that summarises what your contribution does. In some cases Fix <ISSUE TITLE> is enough. Fix #<ISSUE NUMBER> is not enough.

  • All public methods should have informative docstrings with sample usage presented as doctests when appropriate.

  • At least one paragraph of narrative documentation with links to references in the literature (with PDF links when possible) and the example.

  • All functions and classes must have unit tests. These should include, at the very least, type checking and ensuring correct computation/outputs.

  • Ensure all tests are passing locally using pytest. Install the necessary packages by:

    $ pip install pytest pytest-cov

    then run

    $ pytest

    or you can run pytest on a single test file by

    $ pytest path/to/
  • Run an autoformatter to conform to PEP 8 style guidelines. We use black and would like for you to format all files using black. You can run the following lines to format your files.

    $ pip install black
    $ black path/to/


Coding Guidelines

Uniformly formatted code makes it easier to share code ownership. mvlearn package closely follows the official Python guidelines detailed in PEP8 that detail how code should be formatted and indented. Please read it and follow it.

Docstring Guidelines

Properly formatted docstrings is required for documentation generation by Sphinx. The pygraphstats package closely follows the numpydoc guidelines. Please read and follow the numpydoc guidelines. Refer to the provided by numpydoc.

API of mvlearn Objects


The main mvlearn object is the estimator and its documentation draws mainly from the formatting of sklearn’s estimator object. An estimator is an object that fits a set of training data and generates some new view of the data. Each module in mvlearn contains a main base class (found in module_name.base) which all estimators in that module should implement. Each of these base classes implements sklearn.base.BaseEstimator. If you are contributing a new estimator, be sure that it properly implements the base class of the module it is contained within.

When contributing, borrow from sklearn requirements as much as possible and utilize their checks to automatically check the suitability of inputted data, or use the checks available in mvlearn.utils such as check_Xs.


An estimator object’s __init__ method may accept constants that determine the behavior of the object’s methods. These constants should not be the data nor should they be data-dependent as those are left to the fit method. All instantiation arguments are keyworded and have default values. Thus, the object keeps these values across different method calls. Every keyword argument accepted by __init__ should correspond to an instance attribute and there should be no input validation logic on instantiation, as that is left to fit. A correct implementation of __init__ looks like

def __init__(self, param1=1, param2=2):
    self.param1 = param1
    self.param2 = param2


All estimators should implement the fit(Xs, y=None) method to make some estimation, which is called with:, y)


The former case corresponds to the supervised case and the latter to the unsupervised case. In unsupervised cases, y takes on a default value of None and is ignored. Xs corresponds to a list of data matrices and y to a list of sample labels. The samples across views in Xs and y are matched. Note that data matrices in Xs must have the same number of samples (rows) but the number of features (columns) may differ.

Parameters Format
list of array-likes:
  • Xs shape: (n_views,)
  • Xs[i] shape: (n_samples, n_features_i)
y array, shape (n_samples,)
kwargs optional data-dependent parameters.

The fit method should return the object (self) so that simple one line processes can be written.

All attributes calculated in the fit method should be saved with a trailing underscore to distinguish them from the constants passes to __init__. They are overwritten every time fit is called.

Additional Functionality

Transformers and Predictors

A transformer object modifies the data it is given. An estimator may also be a transformer that learns the transformation parameters. The transformer object implements the transform method, i.e.

new_data = transformer.transform(Xs)

or if the fit method must be called first,

new_data = transformer.fit_transform(Xs, y)

It may be more efficient in some cases to compute the latter example rather than call fit and transform separately.

Similarly, a predictor object makes predictions based on the data it is given. An estimator may also be a predictor that learns the prediction parameters. The predictor object implements the predict method, i.e.

predictions = predictor.predict(Xs)

or if the fit method must be called first,

predictions = predictor.fit_predict(Xs, y)

It may be more efficient in some cases to compute the latter example rather than call fit and predict separately.