Add type annotations

[crepererum]

Abstract

We use types in our documentation but it would be better to provide proper annotations.

Example

From:

def add(a, b):
    """
    Adds to numbers.

    Parameters
    ----------
    a: Union[float, int]
        First number to add.
    b: Union[float, int]
        Second number to add.

    Returns
    -------
    c: float
        Sum of both.
    """
    ...

To:

from typing import Union


def add(a: Union[float, int], b: Union[float, int]) -> float:
    """
    Adds to numbers.

    Parameters
    ----------
    a:
        First number to add.
    b:
        Second number to add.

    Returns
    -------
    c:
        Sum of both.
    """
    ...

Please note the colons and new lines after the parameter and return value names, otherwise, sphinx docs break (sphinx will treat your docs as types).