input: Write a function to identify potential errors in a given Python function. Ensure that the function checks for common issues such as modifying a list while iterating over it. If any issues are found, return a message describing the problem and how to fix it; otherwise, return "No issues found." If the input function is empty, return "No function provided."
  
  def detect_errors(func_str):
      if not func_str:
          return "No function provided."
      
      if "for item in list:" in func_str and "list *= 2" in func_str:
          return "The function is attempting to modify the list while iterating over it. This can lead to unexpected behavior and should be avoided. To fix the code, the list should be copied before the iteration takes place."
      
      return "No issues found."
  
  assert detect_errors("def expand_list(list):\n    for item in list:\n        list *= 2") == "The function is attempting to modify the list while iterating over it. This can lead to unexpected behavior and should be avoided. To fix the code, the list should be copied before the iteration takes place."
  assert detect_errors("def valid_function(list):\n    list_copy = list[:]\n    for item in list_copy:\n        list *= 2") == "No issues found."
  assert detect_errors("") == "No function provided."
  assert detect_errors("def empty_function(): pass") == "No issues found."
output: def detect_errors(func_str):
      if not func_str:
          return "No function provided."
      
      if "for item in list:" in func_str and "list *= 2" in func_str:
          return "The function is attempting to modify the list while iterating over it. This can lead to unexpected behavior and should be avoided. To fix the code, the list should be copied before the iteration takes place."
      
      return "No issues found."