input: Write a python function to remove spaces from a string.
  assert remove_spaces("this is a sample sentence") == "thisisasamplesentence"
  assert remove_spaces("  leading and trailing spaces  ") == "leadingandtrailingspaces"
  assert remove_spaces("no spaces") == "nospaces"
output: def remove_spaces(s: str) -> str:
      return s.replace(" ", "")