Add all callbacks to documentation (#2067)

---------

Co-authored-by: Margaret Duff <43645617+MargaretDuff@users.noreply.github.com>

Wrappers/Python/cil/optimisation/utilities/callbacks.py

@@ -147,7 +147,7 @@ class EarlyStoppingObjectiveValue(Callback):
     -----
     This callback only compares the last two calculated objective values. If `update_objective_interval` is greater than 1, the objective value is not calculated at each iteration (which is the default behaviour), only every `update_objective_interval` iterations.
     
-        '''
+    '''
     def __init__(self, threshold=1e-6):
         self.threshold=threshold
 
@@ -160,6 +160,7 @@ def __call__(self, algorithm):
 class CGLSEarlyStopping(Callback):
     '''Callback to work with CGLS. It causes the algorithm to terminate if  :math:`||A^T(Ax-b)||_2 < \epsilon||A^T(Ax_0-b)||_2` where `epsilon` is set to default as '1e-6', :math:`x` is the current iterate and :math:`x_0` is the initial value. 
     It will also terminate if the algorithm begins to diverge i.e. if :math:`||x||_2> \omega`, where `omega` is set to default as 1e6. 
+    
     Parameters
     ----------
     epsilon: float, default 1e-6 

docs/source/optimisation.rst

@@ -598,7 +598,7 @@ In addition, we provide a random sampling class which is a child class of  `cil.
 Callbacks
 ---------
 
-A list of :code:`Callback` s to be executed each iteration can be passed to `Algorithms`_ :code:`run` method.
+A list of :code:`Callback` s to be executed each iteration can be passed to `Algorithm`'s :code:`run` method.
 
 .. code-block :: python
 
@@ -620,6 +620,12 @@ Built-in callbacks include:
 .. autoclass:: cil.optimisation.utilities.callbacks.LogfileCallback
    :members:
 
+.. autoclass:: cil.optimisation.utilities.callbacks.EarlyStoppingObjectiveValue
+   :members:
+
+.. autoclass:: cil.optimisation.utilities.callbacks.CGLSEarlyStopping
+   :members:
+
 Users can also write custom callbacks.
 
 Below is an example of a custom callback implementing early stopping.