InsertLocked(key, *value);
    }
  }

  /// Clear the cache.
  void Clear() {
    absl::MutexLock lock(&mu_);
    cache_.clear();
    lru_list_.clear();
  }

  /// Accessors for cache parameters.
  uint64_t max_age() const { return max_age_; }
  size_t max_entries() const { return max_entries_; }

 private:
  struct Entry {
    /// The timestamp (seconds) at which the entry was added to the cache.

#include "tensorflow/c/eager/unified_api_testutil.h"

namespace tensorflow {
namespace gradients {

/* Returns numerical grad inside `dtheta_approx` given `forward` model and
 * parameter specified by `input_index`.
 *
 * I.e. if y = <output of the forward model> and w = inputs[input_index],
 * this will calculate dy/dw numerically.
 *

// Represents a (partially-defined) shape.
typedef struct TF_Shape {
  int num_dims;  // Must be >= -1; -1 represents unknown rank.
  int64_t* dim_sizes;
} TF_Shape;

// Add a new parameter to a TensorFlow Function.
TF_AbstractTensor* TF_AddFunctionParameter(TF_ExecutionContext* func,
                                           TF_DataType dtype, TF_Shape shape,
                                           TF_Status* s);

#include "tensorflow/core/platform/status.h"

namespace tensorflow {

// Builds and returns a `TracingContext` using the default tracing impl.
AbstractContext* BuildFunction(const char* fn_name);

// Creates parameters (placeholders) in the tracing `ctx` using the shape and
// dtype of `inputs`.
Status CreateParamsForInputs(AbstractContext* ctx,
                             absl::Span<AbstractTensorHandle* const> inputs,

class TracingContext : public AbstractContext {
 protected:
  explicit TracingContext(AbstractContextKind kind) : AbstractContext(kind) {}

 public:
  // Add a function parameter and return the corresponding tensor.
  virtual Status AddParameter(DataType dtype, const PartialTensorShape& shape,
                              TracingTensorHandle**) = 0;