code: def mtx_refl(nv, reps=1):
      
  
      # Imports
      import numpy as np
      from scipy import linalg as spla
      from ..const import PRM
  
      # Ensure |nv| is large enough for confident directionality
      if spla.norm(nv) < PRM.ZERO_VEC_TOL:
          raise ValueError("Norm of 'nv' is too small.")
      ## end if
  
      # Ensure nv is a normalized np.float64 3-vector
      nv = make_nd_vec(nv, nd=3, t=np.float64, norm=True)
  
      # Ensure reps is a positive scalar integer
      if not np.isscalar(reps):
          raise ValueError("'reps' must be scalar.")
      ## end if
      if not np.issubdtype(type(reps), int):
          raise ValueError("'reps' must be an integer.")
      ## end if
      if not reps > 0:
          raise ValueError("'reps' must be a positive integer.")
      ## end if
  
      # Initialize the single-point reflection transform matrix
      base_mtx = np.zeros(shape=(3,3), dtype=np.float64)
  
      # Construct the single-point transform matrix
      for i in range(3):
          for j in range(i,3):
              if i==j:
                  base_mtx[i,j] = 1 - 2*nv[i]**2
              else:
                  base_mtx[i,j] = base_mtx[j,i] = -2*nv[i]*nv[j]
              ## end if
          ## next j
      ## next i
  
      # Construct the block-diagonal replicated reflection matrix
      refl_mtx= spla.block_diag(*[base_mtx for i in range(reps)])
  
      # Return the result
      return refl_mtx
docs: Generate block-diagonal reflection matrix about nv.
  
      reps must be >=1 and indicates the number of times the reflection
      matrix should be repeated along the block diagonal.  Typically this
      will be the number of atoms in a geometry.
  
      .. todo:: Complete mtx_refl docstring