code: def _flat(params):
      """
      converts a nested parameter list into flat parameter list
  
      Inputs:
          params -- a nested list of weights or positions
  
      Examples:
          >>> par = [['x','x','x'], ['y','y'], ['z']]
          >>> _flat(par)
          ['x','x','x','y','y','z']"""
      from mystic.tools import flatten
  
      return list(flatten(params))
  
imports: from mystic.math.stats import *
  from mystic.math.samples import *
  from mystic.math.integrate import *
  from mystic.symbolic import generate_solvers, generate_constraint, solve
  from mystic.symbolic import generate_conditions, generate_penalty
  from mystic.math import almostEqual
  from mystic.math.distance import Lnorm
  from numpy import asarray
label_desc: Use image node_id 57 for calling a global function with example usage: _flat(params) and returns: list