code: def generate_contrast(problem):
      """Generates the raw sample from the problem file.
  
      Parameters
      ----------
      problem : dict
          The problem definition
      """
  
      num_vars = problem["num_vars"]
  
      # Find the smallest n, such that num_vars < k
      k_chosen = 2 ** find_smallest(num_vars)
  
      # Generate the fractional factorial contrast
      contrast = np.vstack([hadamard(k_chosen), -hadamard(k_chosen)])
  
      return contrast
  
file_path: SALib/src/SALib/sample/ff.py
imports: from scipy.linalg import hadamard
  import numpy
  from .None import common_args
  from ..util import scale_samples, read_param_file
label_desc: Use image node_id 3 for calling a global function with example usage: generate_contrast(problem) and returns: contrast