masking demo (#29)

* made client slightly more robust to funny inputs

* added masking demo

* version bump

setup.py

@@ -5,7 +5,7 @@
 
 setup(
  name='stability-sdk',
- version='0.2.0',
+ version='0.2.1',
  author='Wes Brown',
  author_email='[email protected]',
  maintainer='David Marx',

src/stability_sdk/client.py

@@ -236,10 +236,10 @@ def generate(
  if safety and classifiers is None:
  classifiers = generation.ClassifierParameters()
 
- if not prompt and not init_image:
+ if (prompt is None) and (init_image is None):
  raise ValueError("prompt and/or init_image must be provided")
 
- if mask_image and not init_image:
+ if (mask_image is not None) and (init_image is None):
  raise ValueError("If mask_image is provided, init_image must also be provided")
 
  request_id = str(uuid.uuid4())
@@ -256,7 +256,7 @@ def generate(
  else:
  raise TypeError("prompt must be a string or a sequence")
 
- if init_image:
+ if (init_image is not None):
  prompt += [image_to_prompt(init_image, init=True)]
  parameters = generation.StepParameter(
  scaled_step=0,
@@ -268,7 +268,7 @@ def generate(
  end=end_schedule,
  )
  ),
- if mask_image:
+ if (mask_image is not None):
  prompt += [image_to_prompt(mask_image, mask=True)]
  else:
  parameters = generation.StepParameter(