<human>:  Python function for a lower each dict key.
<bot>: Here is a Python function for a lower each dict key

import numpy as np

def lower_dict_keys(d):
  """Lower each dict key.

  Args:
   d (dict): dict

  Returns:
   dict: dict with all keys lowercased
  """
  return {k.lower(): v for k, v in list(d.items())}

# Enter the dict
d = {"a": 1, "b": 2, "c": 3}

# Calling the function
print((lower_dict_keys(d)))

#Example Output
# {'a': 1, 'b': 2, 'c': 3}

#Remember to inspect code for bugs.