code: 
  '''simple docstring'''
  
  
  
  def  _A		(							lowercase__	):
  						if not isinstance(lowercase__		,		lowercase__	):
  												raise ValueError("""Input series is not valid, valid series - [1, 2/3, 2]"""	)
  						if len(lowercase__	) == 0:
  												raise ValueError("""Input list must be a non empty list"""	)
  						if len(lowercase__	) == 1 and series[0] != 0:
  												return True
  						lowercase__							 =       []
  						lowercase__							 =       len(lowercase__	)
  						for i in range(0		,		lowercase__	):
  												if series[i] == 0:
  																		raise ValueError("""Input series cannot have 0 as an element"""	)
  												rec_series.append(1 / series[i]	)
  						lowercase__							 =       rec_series[1] - rec_series[0]
  						for index in range(2		,		lowercase__	):
  												if rec_series[index] - rec_series[index - 1] != common_diff:
  																		return False
  						return True
  
  
  
  
  
  def  _A		(							lowercase__	):
  						if not isinstance(lowercase__		,		lowercase__	):
  												raise ValueError("""Input series is not valid, valid series - [2, 4, 6]"""	)
  						if len(lowercase__	) == 0:
  												raise ValueError("""Input list must be a non empty list"""	)
  						lowercase__							 =       0
  						for val in series:
  												answer += 1 / val
  						return len(lowercase__	) / answer
  
  
  if __name__ == "__main__":
  				import doctest
  
  				doctest.testmod()
  
  
  
  
  
  
  
style_context: 
  '''simple docstring'''
  
  
  
  def  _A		(							lowercase__	):
  
  						# validate:
  						if not isinstance(lowercase__		,		lowercase__	) or not all(
  						    isinstance(lowercase__		,		lowercase__	) and item >= 0 for item in citations	):
  												raise ValueError("""The citations should be a list of non negative integers."""	)
  
  						citations.sort()
  						lowercase__							 =       len(lowercase__	)
  
  						for i in range(lowercase__	):
  												if citations[len_citations - 1 - i] <= i:
  																		return i
  
  						return len_citations
  
  
  if __name__ == "__main__":
  				import doctest
  
  				doctest.testmod()
  
  
  
  
  
  
  