Galaxy / Tracer#

`Galaxy`	Class representing a galaxy, which is composed of attributes used for fitting galaxies (e.g.
`Galaxies`	A collection of galaxies, used to perform operations on the galaxies as a group.
`Tracer`	Performs gravitational lensing ray-tracing calculations based on an input list of galaxies and a cosmology.

To treat the redshift of a galaxy as a free parameter in a model, the Redshift object must be used.

This is because PyAutoFit (which handles model-fitting), requires all parameters to be a Python class.

The Redshift object does not need to be used for general PyAutoGalaxy use.

Class used when assigning a redshift to a Galaxy object.