docstr: Converts MutableDenseNDimArray to Matrix. Can convert only 2-dim array, else will raise error.
  
  Examples
  ========
  
  >>> from sympy import MutableSparseNDimArray
  >>> a = MutableSparseNDimArray([1 for i in range(9)], (3, 3))
  >>> b = a.tomatrix()
  >>> b
  Matrix([
  [1, 1, 1],
  [1, 1, 1],
  [1, 1, 1]])
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code: def tomatrix(self):
      """
      Converts MutableDenseNDimArray to Matrix. Can convert only 2-dim array, else will raise error.
  
      Examples
      ========
  
      >>> from sympy import MutableSparseNDimArray
      >>> a = MutableSparseNDimArray([1 for i in range(9)], (3, 3))
      >>> b = a.tomatrix()
      >>> b
      Matrix([
      [1, 1, 1],
      [1, 1, 1],
      [1, 1, 1]])
      """
      from sympy.matrices import SparseMatrix
  
      if self.rank() != 2:
          raise ValueError("Dimensions must be of size of 2")
  
      mat_sparse = {}
      for key, value in self._sparse_array.items():
          mat_sparse[self._get_tuple_index(key)] = value
  
      return SparseMatrix(self.shape[0], self.shape[1], mat_sparse)
  
imports: from sympy.core.basic import Basic
  from sympy.core.containers import Dict, Tuple
  from sympy.core.singleton import S
  from sympy.core.sympify import _sympify
  from sympy.tensor.array.mutable_ndim_array import MutableNDimArray
  from sympy.tensor.array.ndim_array import NDimArray, ImmutableNDimArray
  from sympy.utilities.iterables import flatten
  import functools
label_desc: Use image node_id 4 for calling the SparseNDimArray obj's underlying member method code with example usage: obj.tomatrix() and returns: SparseMatrix