code: def _convert_string_aliases(deriv, target_shape):
      if isinstance(deriv, str):
          if deriv == "clamped":
              deriv = [(1, np.zeros(target_shape))]
          elif deriv == "natural":
              deriv = [(2, np.zeros(target_shape))]
          else:
              raise ValueError(
                  "Unknown boundary condition : %s" % deriv
              )
      return deriv
  
imports: import operator
  from math import prod
  import numpy
  from scipy._lib._util import normalize_axis_index
  from scipy.linalg import get_lapack_funcs, LinAlgError, cholesky_banded, cho_solve_banded, solve, solve_banded
  from scipy.optimize import minimize_scalar
  from .None import _bspl
  from .None import _fitpack_impl
  from scipy.sparse import csr_array
  from scipy.special import poch
  from itertools import combinations
label_desc: Use image node_id 7 for calling a global function with example usage: _convert_string_aliases(deriv, target_shape) and returns: deriv