input: Write a function to generate a data visualization dashboard using Matplotlib in Python. The function should create a simple line plot with a specified title and axis labels using the given data points. If the data is invalid (such as an empty list or incorrect input type), the function should return an error message.
  
  assert generate_dashboard([1,2,3,4,5], [10,25,30,50,80]) == None # Plot displayed without error
  assert generate_dashboard(['a', 'b'], [1, 2]) == "Invalid input" # Invalid data type
  assert generate_dashboard([], []) == "No data to plot" # Empty data list
output: def generate_dashboard(x_data, y_data):
      if not isinstance(x_data, list) or not isinstance(y_data, list):
          return "Invalid input"
      if len(x_data) == 0 or len(y_data) == 0:
          return "No data to plot"
      if not all(isinstance(i, (int, float)) for i in x_data) or not all(isinstance(i, (int, float)) for i in y_data):
          return "Invalid input"
      
      import matplotlib.pyplot as plt
      plt.plot(x_data, y_data)
      plt.title('Simple Line Plot')
      plt.xlabel('X-axis')
      plt.ylabel('Y-axis')
      plt.show()