in src/stepfunctions/inputs/placeholders.py [0:0]
def _create_variable(self, name, parent, type=None):
"""
Creates a placeholder variable for Workflow Input.
A placeholder variable can only be created if the collection is not immutable due to a pre-specified schema.
"""
if self.immutable:
raise ValueError("Placeholder variable does not conform to schema set for the placeholder collection.")
if type:
return ExecutionInput(name=name, parent=parent, type=type)
else:
return ExecutionInput(name=name, parent=parent)