Removed Constant step method

Author: fonnesbeck

pymc3/step_methods/__init__.py

@@ -16,6 +16,4 @@
 
 from .slicer import Slice
 
-from .nuts import NUTS
-
-from .arraystep import Constant
+from .nuts import NUTS

pymc3/step_methods/arraystep.py

@@ -8,7 +8,7 @@
 from enum import IntEnum, unique
 
 __all__ = ['ArrayStep', 'ArrayStepShared', 'metrop_select', 'SamplerHist',
-           'Competence', 'Constant']
+           'Competence']
 
 
 @unique
@@ -163,30 +163,3 @@ def __init__(self):
     def acceptr(self):
         return np.minimum(np.exp(self.metrops), 1)
 
-
-class Constant(ArrayStep):
-    """
-    Dummy sampler that returns the current value at every iteration. Useful for
-    fixing parameters at a particular value.
-
-    Parameters
-    ----------
-    vars : list
-        List of variables for sampler.
-    model : PyMC Model
-        Optional model for sampling step. Defaults to None (taken from context).
-    """
-
-    def __init__(self, vars, model=None, **kwargs):
-
-        model = modelcontext(model)
-
-        self.model = model
-
-        vars = inputvars(vars)
-
-        super(Constant, self).__init__(vars, [model.fastlogp], **kwargs)
-
-    def astep(self, q0, logp):
-
-        return q0