message: Check df parameter > 0 for Chi2.
diff: @@ -21,6 +21,8 @@ from __future__ import print_function
  from tensorflow.python.framework import constant_op
  from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import ops
  +from tensorflow.python.ops import array_ops
  +from tensorflow.python.ops import check_ops
  from tensorflow.python.ops import math_ops
  from tensorflow.python.ops.distributions import gamma
  @@ -87,7 +89,11 @@ class Chi2(gamma.Gamma):
  # allow_nan_stats=True
  # through to the parent class results in unnecessary asserts.
  with ops.name_scope(name, values=[df]):
  - self._df = ops.convert_to_tensor(df, name="df")
  + with ops.control_dependencies([
  + check_ops.assert_positive(df),
  + ] if validate_args else []):
  + self._df = array_ops.identity(df, name="df")
  +
  super(Chi2, self).__init__(
  concentration=0.5 * self._df,
  rate=constant_op.constant(0.5, dtype=self._df.dtype),
  