code: def _mul_vector(self, other):
      # matrix * vector
      result = np.zeros(
          self.shape[0], dtype=upcast(self.dtype, other.dtype)
      )
      for (i, j), v in self.items():
          result[i] += v * other[j]
      return result
  
imports: import itertools
  import numpy
  from ._matrix import spmatrix
  from ._base import _spbase, sparray, issparse
  from ._index import IndexMixin
  from ._sputils import isdense, getdtype, isshape, isintlike, isscalarlike, upcast, upcast_scalar, check_shape
label_desc: Use image node_id 32 for calling the _dok_base obj's underlying member method code with example usage: obj._mul_vector(other) and returns: result