class_docstr: Calculates time from a value to a specified cutoff datetime.
  
  Args:
      unit (str): Defines the unit of time to count from.
          Defaults to Seconds. Acceptable values:
          years, months, days, hours, minutes, seconds, milliseconds, nanoseconds
  
  Examples:
      >>> from datetime import datetime
      >>> time_since = TimeSince()
      >>> times = [datetime(2019, 3, 1, 0, 0, 0, 1),
      ...          datetime(2019, 3, 1, 0, 0, 1, 0),
      ...          datetime(2019, 3, 1, 0, 2, 0, 0)]
      >>> cutoff_time = datetime(2019, 3, 1, 0, 0, 0, 0)
      >>> values = time_since(times, time=cutoff_time)
      >>> list(map(int, values))
      [0, -1, -120]
  
      Change output to nanoseconds
  
      >>> from datetime import datetime
      >>> time_since_nano = TimeSince(unit='nanoseconds')
      >>> times = [datetime(2019, 3, 1, 0, 0, 0, 1),
      ...          datetime(2019, 3, 1, 0, 0, 1, 0),
      ...          datetime(2019, 3, 1, 0, 2, 0, 0)]
      >>> cutoff_time = datetime(2019, 3, 1, 0, 0, 0, 0)
      >>> values = time_since_nano(times, time=cutoff_time)
      >>> list(map(lambda x: int(round(x)), values))
      [-1000, -1000000000, -120000000000]
code: def __init__(self, unit="seconds"):
      self.unit = unit.lower()
  
file_path: featuretools/featuretools/primitives/standard/transform/datetime/time_since.py
imports: from woodwork.column_schema import ColumnSchema
  from woodwork.logical_types import Datetime
  from featuretools.primitives.base import TransformPrimitive
  from featuretools.utils import convert_time_units
  from featuretools.utils.gen_utils import Library
label_desc: Use image node_id 1 to create a new TimeSince object from inherited base classes: TransformPrimitive with example: obj = TimeSince(unit)