input: Write a python function to perform a left circular rotation on a given string.
  assert left_circular_rotation("python",2) == "thonpy"  
  assert left_circular_rotation("bigdata",3 ) == "databig"  
  assert left_circular_rotation("hadoop",1 ) == "adooph"
output: 
  def left_circular_rotation(s, n):
      n = n % len(s)
      return s[n:] + s[:n]
  