code: def _to_string_matrix(num_matrix):
      str_matrix = ""
      for i, row in enumerate(num_matrix):
          for j, elem in enumerate(row):
              str_matrix += str(elem)
              if j < num_matrix.shape[1] - 1:
                  str_matrix += " "
              elif i < num_matrix.shape[0] - 1:
                  str_matrix += "; "
      return str_matrix
  
imports: from hypothesis import assume, strategies
  import numpy
  import sys
  import ivy
  import ivy_tests.test_ivy.helpers
  from ivy_tests.test_ivy.helpers import handle_frontend_method, handle_frontend_test
  import ivy.functional.frontends.numpy
label_desc: Use image node_id 3 for calling a global function with example usage: _to_string_matrix(num_matrix) and returns: str_matrix